Modal verbs are used to express meanings like ability, permission, certainty, possibility, advice, obligation, and prohibition when combined with other verbs. There are several types of modal verbs including: ability (can, could), permission/request (can, could, may), certainty/possibility (must, may, might), advice (should, ought to), obligation (must, have to), and prohibition (mustn't). Modal verbs are followed by the base form or have + past participle form of other verbs and can be used in positive, negative, or interrogative sentences. Modal perfects are also used to express meanings like certainty, possibility, ability, criticism, and lack of necessity about past events.

1. MODAL VERBSMODAL VERBS

2. 1. They are verbs like can, must, might, etc… which give
certain meanings to main verbs.
You smoke. / You shouldn’t smoke. / You mustn’t smoke.
2. They are followed by either:
– base form of the verb. I should tell him the truth.
– have + past participle form of the verb. I should have told
him the truth.
3. Structure:
(+) We should stay.
(-) We shouldn't stay.
(?) Should we stay?

3. 4. Types of Modal verbs:
ABILITY: can / could / *be able to
PERMISSION & REQUEST: can / could / may
CERTAINTY & LOCAL DEDUCTION: must / can’t
PROBABILITY & POSSIBILITY: can / could / may / might

4. ADVICE: should / ought to
OBLIGATION: must / *have to / need to
LACK OF OBLIGATION: don’t have to / don't need to / needn’t
PROHIBITION: mustn’t

5. ABILITY (can, could & *be able to)
1. Present: can
Two of my friends can play the guitar.
2. Past: could
When he was a child he could ski well.
3. Other tenses: be able to
- There was a fire and I was able to escape out (= I
managed to escape out) of the room. (specific situation in
the past)
- Next week they'll be able to vote. (future)
- We haven't been able to go on holiday this year. (present
perfect)

6. PERMISSION & REQUEST
(can, could & may)
Can you help me?
Could you send me your picture?
May I use your phone? (a bit more polite)

7. CERTAINTY / POSSIBILITY
(must , can’t & couldn't / could, may & might)
CERTAINTY POSSIBILITY
1. 100% SURE +
They must be an item. I’ve seen them
kissing.
(I totally believe this)
3. 80% - 30% % SURE + / -
They could / may / might be an item.
They’re good friends and…
They may not / might not be an item.
Some people say so ,but I’m not sure…
We can invite Jim to the party.
(Why not?)
We could / may invite Jim to the party.
(Not so sure…)
We might invite Jim to the party.
(Could be but I don’t think so…)
2. 100% SURE -
They can’t be an item. They don’t get
along.
( I don’t believe it)

8. ADVICE
(should / ought to)
You should / ought to study more for your exams.
You shouldn’t smoke.
* Ought to rarely seen in negatives or questions.

9. OBLIGATION / LACK OF OBLIGATION / PROHIBITION
OBLIGATION LACK OF OBLIGATION
HAVE TO // NEED TO DON’T HAVE TO /NEED TO // NEEDN’T
1. OBLIGATION which comes from sb else. It’s a
law or a rule and the speaker can’t change it.
In Britain you have to /need to buy a TV licence
every year.
She has to / needs to wear a school uniform.
You don’t have to / need to //needn’t order your
meal now.
She doesn’t have to / need to // needn’t cook
dinner tonight.
2. OBLIGATION with other verbal tenses:
I ‘ll have to pass those exams to go to university.
We had to leave early.
MUST PROHIBITION
3. OBLIGATION which comes from the speaker.
It isn’t a law or a rule.
I must call my dad tonight.
You must try some of this ice-cream.
(suggestion & recommendation)
MUSTN’T
You mustn’t drink and drive.

10. 5. Types of Modal Perfects:
CERTAINTY ABOUT sth: must have / can’t have
Danny must have felt disappointed when he didn't win the prize.
She can't have passed the exam, she didn't study at all.
POSSIBILITY ABOUT sth : may / might / could have
He may / might have gone to the cinema
The situation is bad but it could have been worse. (it was possible
but it didn't happen)

11. ABILITY TO HAVE DONE sth (BUT NOT DONE): could have
He could have helped us, but he came too late.
CRITICISM / REGRET AFTER AN EVENT: should / ought to have
She should have seen a doctor…She’s worse today.
You should / ought to have come to the party
Linda shouldn't have talked so much

12. NOT NECESSARY: needn’t have
Everything was ok. You needn’t have worried. (you worried but it
was not necessary)