Grammar / Modal Verbs
Modal Verbs: Explanation, Examples & Exercises
Modal verbs — can, could, may, might, must, should, will, would — add meaning such as ability, permission, possibility, obligation and advice. They are followed by the base verb with no to (You should rest), never take -s in the third person, and form questions and negatives without do.
Reviewed by Brando Oxley · 9 Aug 2026
Form
A modal is always followed by the base form of the verb, with no to: I can help. She must leave. (Not: She must to leave.)
Modals never add -s in the third person: He can swim. It might rain. (Not: He cans.)
Make questions by putting the modal first: Can you help? Should I call them?
Make negatives by adding not to the modal: cannot / can't, must not / mustn't, should not / shouldn't, might not.
Modals have no past -ed and no infinitive. For meanings they can't cover we use other phrases: have to (obligation), be able to (ability), be allowed to (permission).
have to is not a true modal: it takes do in questions and negatives — Do you have to work? I don't have to go.
How it is used
Ability: can and could — I can drive. She could read at four.
Permission and requests: can, could, may — Could you send me the file? May I leave early?
Possibility: may, might, could — It might rain later. This could be a problem.
Obligation and necessity: must and have to — You must wear a badge. I have to finish this today.
Advice and recommendation: should and ought to — You should see a doctor. We should book early.
No obligation vs prohibition: don't have to (not necessary) is very different from mustn't (forbidden): You don't have to come vs You mustn't smoke here.
Common errors
✗She can to drive.
✓She can drive.
After a modal, use the base verb with no to.
✗He cans speak three languages.
✓He can speak three languages.
Modals never take -s in the third person.
✗You must not to be late.
✓You must not be late.
Not goes straight after the modal, and the verb has no to.
✗Do you can help me?
✓Can you help me?
Modals form questions on their own — no do.
✗You don't must park here.
✓You mustn't park here.
The negative of must is mustn't; don't goes with have to, not must.
Example sentences
Ability and requests
- I can start the project on Monday.
- Could you email me the agenda?
- She can speak both French and German.
Possibility and advice
- The meeting might finish early today.
- You should back up your files regularly.
- It could be cheaper to book online.
Obligation and prohibition
- Visitors must sign in at the desk.
- You don't have to stay until the end.
- Staff mustn't share their passwords.
Exercise 1 — Fill the gaps
Complete each sentence, then tap to check your answer.
1.· you send me the report by five?(polite request)
2.You look tired — you · take a break.(advice)
3.He · speak three languages fluently.(ability)
4.All staff · wear an ID badge in the building.(obligation)
5.It · rain later, so take an umbrella.(possibility)
6.You · park here — it's for deliveries only.(prohibition)
7.It's optional, so you · work on Saturday.(not necessary)
Exercise 2 — Choose the correct form
Tap an option to check it immediately.
1.She ____ drive, but she prefers the train.
2.You ____ be late for the interview.
3.____ you help me with this form?
4.It's just a suggestion — you ____ come if you're busy.
5.We ____ book early to get a good price.