(can, could, may, might, must, should, will, would) are helping verbs that add meaning such as ability, possibility, permission, advice and obligation. They are always followed by the base verb with no to and never take -s: she can swim, you should go, it may rain.
What modal verbs are and how they work
A comes before another verb and changes its meaning. The main modals are can, could, may, might, must, should, will, would and shall. Phrases such as have to and ought to do similar jobs.
They follow three simple rules. First, the next verb is the base form with no to: you must go, not you must to go. Second, there is no -s for he, she or it: she can, not she cans. Third, for questions and negatives you do not need do: Can you help? You should not worry.
- She can speak three languages. · ability
- Cities should invest in public transport. · advice
Ability and possibility
Use can for present ability and could for general ability in the past: I could swim when I was six. For one particular past success, use was able to: I was able to finish the report on time.
For possibility, the modals form a scale from less to more sure. May, might and could mean it is possible: The economy may slow down. Must means you are almost certain: The lights are off, so they must be out. Can't means you are almost certain it is not true: That can't be the right answer.
Obligation, advice and permission
Use must or have to for obligation. Must often shows the speaker's own opinion (I must study more). Have to usually shows a rule from outside (Students have to wear a uniform). In writing, must sounds strong and is best for rules and urgent needs.
Use should or ought to for advice and recommendations: Governments should reduce taxes on public transport. In Writing Task 2, should is the most useful modal for giving your opinion without sounding rude.
Use can, may or could for permission: May I leave the room? is polite; Can I leave? is normal in conversation.
Must not and do not have to are different
This is one of the most important contrasts. Must not means it is forbidden: You must not use a phone in the exam room. Do not have to means it is not necessary, but allowed: You do not have to bring a pen, because one is provided.
If you mix these up, your meaning changes completely. Say them aloud once with a clear example to fix the difference in your head.
Would and shall
Use would for polite requests (Would you mind opening the window?), for imaginary situations (If I had more time, I would learn Italian) and for repeated actions in the past (We would visit my grandmother every Sunday). In reported speech, would is the past of will: She said she would call.
Use shall in British English for offers and suggestions, always with I or we: Shall I open the window? Shall we start? Shall is rare in academic writing, so you can leave it out of your essays.
Modals with the past
To talk about the past with a modal, use modal + have + . This is useful for regrets and guesses. I should have revised more (I did not, and it was a mistake). He must have missed the bus (I am sure that is what happened). She might have forgotten (it is possible).
Do not use the past tense of the main verb after a modal. Say should have gone, not should went.
Hedging in academic writing
Academic writers avoid saying something is always true. They use modals and similar words to be careful: Social media may affect sleep. Cities could reduce pollution by limiting cars. This kind of language is called hedging, and it makes your argument sound balanced and honest.
In IELTS Writing Task 2, mix confident modals (must, will, should) with careful ones (may, might, could), and use each where it fits your real opinion.
Link each modal to a phrase
A useful way to learn modals is to link each one to a function and keep a short phrase ready. For ability: I can manage. For advice: you should try. For possibility: it might work. For obligation: you have to apply. For permission: may I ask? Say the phrases aloud until they feel automatic. In the exam, you will then reach for the right modal without translating, and you will avoid the most common errors with to and -s.
Common mistakes
Check your writing for these:
- You must to submit the form. Say: you must submit the form.
- He cans swim. Say: he can swim.
- She should went home. Say: she should have gone home, or she should go home.
- You mustn't bring a pen. Say: you don't have to bring a pen, if it is not necessary.
- Students can to use the library. Say: students can use the library.
Who finds this hard?
- Arabic speakers: Arabic often expresses these ideas with a full verb plus a second verb or a particle, so you may add to after a modal. Remember: modal + base verb, nothing else.
- Turkish speakers: Turkish puts ability and necessity in verb endings. In English they become separate words that come before the verb, with no to.
- Korean speakers: Korean puts these meanings at the end of the verb. English puts the modal first, so practise saying 'must' or 'should' straight before the main verb.
IELTS tip
In Writing Task 2, use should for your main recommendation and may or could for possible results. In Speaking, try That must be difficult, It might be a good idea and I should have done more to show a natural range of modal meanings.
Frequently asked questions
What are the modal verbs in English?
The main modals are can, could, may, might, must, should, will, would and shall. Ought to, have to and need to are often grouped with them because they have similar meanings.
What is the difference between must and have to?
Must often shows the speaker's opinion or a strong need, while have to usually shows a rule from outside. In the negative they differ more: must not means forbidden, do not have to means not necessary.
Why do modal verbs not take -s?
Modals are special helping verbs with one form for every subject. So it is she can, he must and it may, never she cans.
Which modals should I use in IELTS Writing Task 2?
Use should to give recommendations and may, might or could to show careful possibilities. Use must and will for points you want to state firmly.
Sources
- Swan, M. (2016). Practical English Usage, 4th edition. Oxford University Press.
- Biber, D., Johansson, S., Leech, G., Conrad, S. and Finegan, E. (1999). Longman Grammar of Spoken and Written English. Longman.