What are Modal Verbs?
Modal verbs are auxiliary (helper) verbs used before the base form of another verb. They express ability, possibility, necessity, permission, and more.
Key grammar rules for modals:
- No -s in third person singular: She can swim. (not She cans swim.)
- Followed by bare infinitive (no to): You must go. (not You must to go.)
- Negative: add not after the modal: cannot / can't, must not / mustn't
Modal Verbs and Their Meanings
| Modal | Main meanings | Example |
|---|---|---|
| can | ability; permission (informal) | I can swim. Can I leave? |
| could | past ability; polite request; possibility | She could read at age 4. Could you help me? |
| must | strong necessity; strong deduction | You must wear a helmet. He must be tired. |
| have to | external necessity (rule/law) | We have to wear a uniform at school. |
| should | advice; mild obligation | You should eat more vegetables. |
| ought to | advice (slightly formal) | You ought to apologise. |
| may | formal permission; possibility | You may leave. It may rain. |
| might | weaker possibility | It might be cold tomorrow. |
| shall | offers; suggestions (British) | Shall I open the window? |
| will | future; willingness; certainty | I'll call you later. |
| would | conditional; polite requests; past habit | Would you like tea? I would study every evening. |
| need not | no necessity | You needn't hurry — we have time. |
must vs have to: Must comes from the speaker's own feeling; have to comes from external rules.
- I must tidy my room. (I feel it's necessary)
- I have to tidy my room. (Someone told me to / it's a rule)
Negatives
| Modal | Negative | Contraction |
|---|---|---|
| can | cannot | can't |
| could | could not | couldn't |
| must | must not | mustn't |
| should | should not | shouldn't |
| will | will not | won't |
| would | would not | wouldn't |
- 1
Choose the right meaning
Ability? Permission? Advice? Possibility? - 2
Use modal + base verb
No -s, no -to, no -ing after the modal. - 3
For negatives, add not after modal
can + not = cannot / can't.
Fill in with the correct modal: 'You ___ smoke in the classroom — it is forbidden.' (prohibition)
You must not (mustn't) smoke in the classroom.
Real world: signs and notices
You must wear a seatbelt at all times. (law / road sign) Passengers must not lean out of the window. (train notice) You may not park here between 8 am and 6 pm. (parking sign)
Real world: job advertisement
"Applicants must have at least two years of experience. Candidates should be able to work independently. You will be working in a fast-paced environment. References may be requested."
Real world: doctor's advice
"You should drink at least two litres of water a day. You shouldn't eat too much salt. You might feel tired for a few days, but you don't have to stay in bed. If the pain gets worse, you must call the clinic."
Practice Problems
Fill in: I ___ drive when I was 14. (past ability)
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Fill in: ___ you pass the salt, please? (polite request)
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Fill in: You ___ study tonight — there's no school tomorrow. (no necessity)
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What is the negative contraction of 'should not'?