Modal verbs: certainty, obligation and possibility
Modals let you speculate, recommend and hedge: the three things band 7+ candidates do constantly in Task 2 and Speaking Part 3. Learn the certainty scale (must, might, can't + perfect forms), the strength scale for recommendations, academic hedging, and fix 'should to', 'must went' and 'can able to' for good.
By the end of this lesson you will be able to:
- Use modal grammar correctly: modal + base verb, modal + be + p.p., modal + have + p.p.
- Express degrees of certainty about the present and past with must, may, might, could, can't and their perfect forms
- Choose the right strength for Task 2 recommendations: must, need to, should, ought to, could, don't have to, mustn't
- Hedge claims in academic style ('This may lead to…', 'could arguably', 'is likely to') without over-hedging
- Speculate fluently in Speaking Part 3 and avoid the typical Bangla-influenced modal errors
Modals and your Grammatical Range and Accuracy score
At band 7, the examiner expects a variety of complex structures with frequent error-free sentences. Modal verbs, especially in their perfect and passive forms (could have been avoided, should be restricted), are part of that variety, and they are very easy to check for accuracy. Modals also affect Task Response: a well-hedged position is more convincing than an exaggerated one.
Five grammar rules that never change
The core modals are can, could, may, might, must, shall, should, will, would.
- Modal + base verb (no to, no -s, no -ed, no -ing): should go, not should to go / should goes / should going.
- No -s with he / she / it: She can speak three languages (never cans).
- Never two modals together: will can ✗ → will be able to ✓; might can ✗ → might be able to ✓.
- To talk about the past, use modal + have + past participle: must have gone, not must went.
- Negatives and questions need no do: You shouldn't worry. · Can we change the date?
Semi-modals behave like normal verbs and DO take to: ought to, have to, need to, be able to, had better (no to: You'd better leave).
The six modal patterns you need
| Pattern | Form | IELTS example |
|---|---|---|
Simple | modal + base verb | Governments should invest more in public transport. |
Continuous | modal + be + -ing | Many students may be struggling silently with stress. |
Passive | modal + be + past participle | Advertising of junk food to children should be restricted. |
Perfect | modal + have + past participle | The authorities could have prevented much of the damage. |
Perfect passive | modal + have been + past participle | The disaster could have been avoided with earlier warnings. |
Perfect continuous | modal + have been + -ing | She must have been studying all night; she looks exhausted. |
The certainty scale: speculating about the present and the past
| How sure are you? | Present / future | Past | Example |
|---|---|---|---|
Almost certain it IS true (logical deduction) | must + verb | must have + p.p. | The streets are under water. It must have rained heavily overnight. |
Probable / expected | should, will probably, is likely to | should have + p.p. (expected by now) | Prices are likely to stabilise next year. · The results should have arrived by now. |
Possible (50% or less) | may, might, could | may / might / could have + p.p. | The rise might be due to tourism. · The survey may have been incomplete. |
Possible but did NOT happen | – | could have + p.p. | More lives could have been saved with earlier evacuation. |
Possibly not | may not, might not | may not / might not have + p.p. | The policy might not work in rural areas. |
Almost certain it is NOT true | can't, couldn't | can't / couldn't have + p.p. | That figure can't be right; the percentages add up to 120. · He can't have seen the email; he was offline all day. |
Nobody knows exactly when the old zamindar house in my village was built, but it must be at least 150 years old. The family who lived there must have been extremely wealthy, because the carvings on the pillars are incredibly detailed. Some people say they might have moved to Kolkata around the time of Partition, although it could also have been simply that the house became too expensive to maintain. Today it's in very bad condition, and if nobody restores it, the roof may well collapse within a few years. Honestly, I think it should have been protected as a heritage site decades ago.
- must be at least 150 years oldPresent deduction from evidence: you are confident but you do not know for certain.
- must have been extremely wealthyPast deduction with evidence ('because the carvings…'). Always give the reason for a 'must' deduction; it shows logical thinking.
- might have moved … could also have beenTwo past possibilities, presented as alternatives. This is exactly the 'flexibility' examiners reward.
- may well collapse'May well' / 'might well' / 'could well' = a fairly strong possibility. A natural, high-band collocation.
- should have been protectedModal perfect passive used for criticism: it was the right thing to do, but it did not happen.
Check: form and certainty
7 questions- 1
The streets are completely flooded. It have rained heavily overnight.
- 2
That be Rahim at the door; he's in Chattogram all week.
- 3
Find and correct the mistake:
The ancient city must abandoned after the river changed course.
- 4
I'm not sure why sales fell in 2019. Prices ___ have risen that year.
- 5
Find and correct the mistake:
The official figures maybe wrong.
- 6
Match each sentence to its meaning.
He must have left.He can't have left.He might have left.He should have left earlier. - 7
With better early-warning systems, many more lives could saved.
Answer every question to check.
Obligation and advice: choosing the strength of a recommendation
| Strength | Modal | Meaning | Task 2 / Speaking example |
|---|---|---|---|
Essential | must | The writer's own strong view; rules and laws | Governments must act now to cut carbon emissions. |
Essential (external) | have to / need to | Necessary because of a rule or situation | Students in Bangladesh have to pass the HSC to enter university. · Cities need to plan for rising temperatures. |
Recommended | should / ought to | The right or sensible thing; your main recommendation | Schools should teach financial literacy. · Parents ought to limit screen time. ('ought to' is slightly more formal and less common.) |
A possible option | could / might | A suggestion, one solution among others | One solution could be to introduce congestion charges. |
Not necessary | don't have to / don't need to / needn't | There is no obligation (but you can) | Students don't have to attend every lecture in person. |
Forbidden | mustn't / can't / are not allowed to | Prohibition | Drivers mustn't use their phones while driving. |
Warning (informal) | had better ('d better) | Strong advice with a warning; Speaking only | You**'d better** leave early or you'll miss the bus. |
Past obligation | had to (must has no past form) | It was necessary in the past | Last year we had to pay an extra registration fee. |
Past advice not followed | should have + p.p. | Criticism or regret | The city should have built drainage canals decades ago. |
To tackle congestion in cities such as Dhaka, several measures need to be taken. First and foremost, the government must expand affordable public transport, because roads alone cannot absorb the ever-growing number of private vehicles. The metro rail network should be extended to the outer suburbs, so that commuters do not have to rely on cars and motorbikes. In addition, the authorities could introduce congestion charges in the busiest districts, although such a scheme might prove unpopular at first. If none of these steps is taken, journey times are likely to become even longer, and the economic cost may run into billions of taka every year.
- need to be takenSemi-modal + passive: an impersonal, academic way to introduce solutions.
- must … becauseThe strongest modal is reserved for the most important measure, and it is justified immediately with a reason.
- cannot absorbImpossibility. 'Cannot' (one word) is standard in formal writing; 'can't' is fine in Speaking.
- should be extendedModal passive for the main recommendation. 'Should' is the default recommending modal.
- do not have to relyAbsence of necessity: commuters will no longer need cars. 'Mustn't rely' would mean they are forbidden to, which is wrong.
- could … might prove unpopularA weaker suggestion, then a hedged prediction acknowledging a drawback. This balance strengthens Task Response.
- are likely to … may run intoHedged predictions. 'Will become longer' would be an unprovable absolute claim.
Hedging: from overstated to academic
| ✗ Overstated | ✓ Hedged | Technique |
|---|---|---|
Social media causes depression in teenagers. | Excessive social media use may contribute to depression in some teenagers. | modal + softer verb + limiting quantifier |
This policy will destroy small businesses. | This policy could arguably harm small businesses. | could + arguably |
Online learning is worse than classroom learning. | Online learning may be less effective for younger children. | modal + limited scope |
Everyone agrees that exams are stressful. | It could be argued that exams place unnecessary stress on students. | impersonal modal passive |
Banning cars will solve air pollution. | Restricting cars is likely to reduce pollution, at least in city centres. | is likely to + limiting phrase |
Tourism always damages local culture. | Mass tourism can dilute local traditions. | can = general possibility (sometimes true) |
✗ Over-hedged: It might possibly perhaps be true that… | It may be true that… / This is probably true… | ONE hedge per claim is enough |
Band 6 vs band 8: claiming with control
Band 6: overclaiming
Video games make children violent. Every child who plays these games will become aggressive, so the government must ban all violent games immediately.
Band 8: precise and cautious
Violent video games may encourage aggressive behaviour in some children, particularly when they play for long periods without supervision. Rather than imposing an outright ban, governments would arguably do better to enforce stricter age ratings, which could protect younger players without restricting adults' freedom.
The band 6 version makes three absolute claims ('make', 'every child… will', 'must ban all') that the writer cannot support, which weakens the argument. The band 8 version uses 'may' and 'some children' to limit the claim, 'would arguably do better to' for a measured recommendation, and 'could' inside a relative clause to suggest a benefit. More modals, more nuance, more grammatical range.
Ability and possibility: can, could, be able to
- can / can't: present ability (She can code in Python) and general possibility (Monsoon rain can cause serious flooding: it sometimes does).
- could: general ability in the past (My grandfather could read three languages) and present or future possibility (This could be a turning point).
- was / were able to or managed to: ONE specific success in the past. ✗ Despite the strike, we could reach the exam centre on time. → ✓ we were able to / managed to reach… (In the negative, couldn't is fine for both: We couldn't find a taxi.)
- will be able to: future ability (never will can). Use be able to wherever a modal is grammatically impossible: I'd like to be able to speak French · Since moving here, I have been able to save money.
Modals in Speaking Part 3
Part 3 questions are abstract and often about the future, so you constantly need to speculate and evaluate. Useful frames:
- Predicting: I think it'll probably… · There might well be… · I'd imagine (that)… · I doubt that… will…
- Hypothesising: If I were in charge, I*'d**…* · It would be a mistake to…
- Balancing: That said, it may not be true for everyone. · Of course, it could go the other way.
Q: Do you think people will still read printed books in the future?
I'd imagine they will, but probably far fewer people. E-books are cheaper and you can carry hundreds of them on your phone, so younger readers might well switch completely. That said, printed books may never disappear altogether, because a lot of people, including me, actually enjoy the feel of paper. I suppose they could become a sort of luxury item, a bit like vinyl records.
Modal errors examiners see most often
| ✗ Error | ✓ Correction | Why |
|---|---|---|
Students should to study harder. | Students should study harder. | Modal + base verb, no 'to'. |
He must went home early. | He must have gone home early. (deduction) / He had to go home early. (obligation) | Modals don't change for past; use have + p.p., or 'had to' for past obligation. |
I can able to speak English. | I can speak English. / I am able to speak English. | 'Can' and 'be able to' mean the same; use one. |
People will can work from home. | People will be able to work from home. | No double modals. |
The government should has taken action. | The government should have taken action. | After a modal, 'have' never changes to 'has'. |
The figures maybe wrong. | The figures may be wrong. | 'Maybe' is an adverb; the sentence needs a verb. |
He mustn't be at home; the lights are off. | He can't be at home. | Negative deduction = can't. |
You mustn't bring a pen; we have spares. | You don't have to / needn't bring a pen. | No necessity ≠ prohibition. |
Yesterday I could finish the report on time. | Yesterday I was able to / managed to finish the report. | One specific past success. |
It can rain heavily tomorrow. | It may / might / could rain heavily tomorrow. | Specific future possibility. |
Last year we must pay extra fees. | Last year we had to pay extra fees. | 'Must' has no past form. |
The exam would be held on Monday. (meaning a fact about next week) | The exam will be held on Monday. | In South Asian English 'would' often replaces 'will'. In IELTS, 'would' signals a hypothetical or past-future meaning and can confuse the reader. |
Check: obligation, advice and hedging
7 questions- 1
At most UK universities, students ___ wear a uniform, but they can dress formally if they want to.
- 2
Last year my brother pay a late fee because he submitted his form after the deadline.
- 3
Find and correct the mistake:
The government should to provide free healthcare.
- 4
Which is the best academic version of 'Social media causes depression'?
- 5
Put the parts in order to make a Task 2 recommendation.
Drag the cards (or use the arrows) into the correct order.
- 1to introduce
- 2One solution
- 3congestion charges
- 4could be
- 5in the busiest districts.
- 6
It be argued that congestion charges are unfair to low-income drivers.
- 7
Match each modal to the strength of the recommendation.
Governments must…Governments should…Governments could…Citizens don't have to…
Answer every question to check.
Writing Task 2 practice
120+ words · 15 minWrite ONE body paragraph (the solutions paragraph) for this essay question:
Many young people in developing countries cannot find suitable jobs even after graduating from university. What are the causes of this problem, and what measures could be taken to solve it?
Recommend two or three measures. Vary the strength of your modals (must / need to / should / could), use at least one modal passive, and hedge at least one prediction. Write at least 120 words.
Self-check before submitting
- ☐ A clear topic sentence introducing the solutions
- ☐ At least three different modals or semi-modals of different strength (e.g. need to, should, could)
- ☐ At least one modal passive (should be introduced, need to be taken, could be offered)
- ☐ Every modal followed by a base verb: no 'should to', 'can able to' or 'must went'
- ☐ Each recommendation supported by a reason or an expected result
- ☐ At least one hedged prediction (may, might well, is likely to) rather than an absolute claim
- ☐ A concluding sentence that evaluates the measures
Speaking Part 3 practice
4 questions · up to 90s eachHow do you think cities in Bangladesh will change over the next twenty years?
Listen to the question, then record your answer.
Tips for a band 7+ answer
- • Speculate about the future with 'will probably', 'might well', 'could' and 'I'd imagine…'.
- • Recommend with 'should' and 'need to'; keep 'must' for what is truly essential.
- • Balance your answer: 'That said, it may not be true for everyone.'
- • Use 'can' for general truths only; for specific predictions use may / might / could.
- • Give a reason or example after every speculation so your answer develops naturally.
Final quiz: modal verbs
11 questions- 1
Find and correct the mistake:
In the future, people will can work from anywhere in the world.
- 2
Find and correct the mistake:
I can able to explain this clearly.
- 3
The museum was closed when we arrived. We (should / check) the opening times first.
- 4
Despite the heavy rain, the rescue team ___ reach the village before dark.
- 5
Don't worry about lunch. You bring any food because lunch is provided.
- 6
Which sentence means 'I'm sure he didn't see it'?
- 7
Find and correct the mistake:
The cyclone must caused serious damage to the coastal villages.
- 8
Choose TWO well-hedged claims suitable for a Task 2 essay.
Select 2.
- 9
If emissions are not cut, sea levels well rise by up to a metre by 2100.
- 10
Put the parts in order to make a Speaking Part 3 answer.
Drag the cards (or use the arrows) into the correct order.
- 1disappear
- 2completely.
- 3that printed books
- 4will never
- 5I'd imagine
- 11
Find and correct the mistake:
The exam would be held next Monday, so we need to register now.
Answer every question to check.
Key takeaways
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