Modal verbs are used with other verbs to express meanings like ability, permission, certainty, obligation, and possibility. There are several types of modal verbs including: must and have to which express obligation; should and ought to which give advice; can, could, and be able to which express ability; and may, might, and can which indicate permission or possibility. Modal verbs are usually followed by the base form of other verbs or have plus the past participle form.

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:
ADVICE: should / ought to
OBLIGATION: must / *have to / need to
LACK OF OBLIGATION: don’t have to / don't need to
PROHIBITION: mustn’t
CERTAINTY: must
ABILITY: can / could / *be able to
PERMISSION & REQUEST: can / could / may
PROBABILITY & POSSIBILITY: can / could / may / might

4. 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.

5. OBLIGATION: have to , need to & must
HAVE TO & NEED TO:
1. Obligation which comes from somebody else or 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.
2. Obligation with other verbal tenses – HAVE TO :
I ‘ll have to pass those exams to go to university.
We had to leave early.

6. MUST
1. OBLIGATION which comes from the speaker.
It isn’t a law or a rule.
I must call my dad tonight.
2. Suggestion , recommendation , strong piece of advice:
You must try some of this ice-cream.

7. ●
You don’t have to / need to order your meal now.
●
She doesn’t have to / need to cook dinner tonight.
LACK OF OBLIGATION: don’t have to & don’t need to

8. PROHIBITION: mustn't
You forbid somebody to do something
You mustn’t drink and drive.
You mustn’t lie.

9. CERTAINTY: must
You’re % sure about something. You totally believe it.
They must be an item. I’ve seen them kissing.

10. EXTERNAL OBLIGATION
Have to / Has to
Need to / Needs to
LACK OF OBLIGATION
Don’t have to / don’t need to
Doesn´t have to / doesn’t need to
OBLIGATION WITH OTHER VERBAL
TENSES
Have to (combined with tenses)
PROHIBITION
Mustn’t
INTERNAL OBLIGATION
Must
CERTAINTY
Must
RECOMMENDATION, SUGGESTION…
Must
ADVICE
Should
Shouldn’t

11. 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)

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

13. POSSIBILITY: could, may & might
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…)