Modal Verbs

A. Ability

-> Can / can't / cannot / could (Present /future)
-> Could / couldn't / could not (Past)

Ex.:
- She can play piano.
- They can’t study alone.

B. Possibility

-> May / might / could / may not / might not / could not / couldn’t (Present/future)
-> Might have / may have / could have (past)

Ex.:
- Jane might go to the party.
- Jess may win the competition.

C. Permission

-> Can /can’t / may/ may not

Ex.:
- Teacher, sorry I'm late. May I come in?
- Dad, can I go to the party?

D. Certainty/ Obligation

-> Must / mustn't / must not (present / future)
-> Must have (past)

Ex.:
- You must obey the school's rules.
- Tomorrow you have a Maths test. You must study!

E. Advice

-> Should / shouldn't (present/ future)
-> Should have (past)

Ex.:
- I think you should talk to them.
- Should he go to the doctor?