Modal Verbs

2. A modal verb is a type of auxiliary verb that expresses
possibility, necessity, obligation.
We can use modal verbs with the perfect infinitive to talk
about how sure or unsure we are about something in the
past.

3. HOW DO WE MAKE THE PERFECT
INFINITIVE?
Subject + modal + have + Past participle
•I
•WE
•THEY
•The students
should
can
might
have
gone
played
visited
won

4. Must Have + Past Participle
Usage:
Express a deduction about something that has happened. We feel quite sure
about it.
Examples:
I didn’t hear her voice . She must have gone out.
I cannot find my watch; I must have lost it.
Might/May/Could have + Past Participle
Usage:
Describe a situation when we are not sure about something but we thing it
was possible.
Example:
He may/might have mentioned it, but I can’t really remembered. I wasn’t
listening.
Can’t/couldn’t have + past participle
Usage:
It is used for things that we are sure didn’t happen in the past.
Example:
She can’t have stolen Ann’s bag because she was with me. (It’s impossible)

5. Use must, can’t may/might to rewrite these sentences.
1) I’m almost certain that it happened. – It ____________________.
2) I’m almost certain that it didn’t happen. – It _________________.
3) I’m not sure whether it happened or not. – It ________________.
EXERCISE

6. Should Have + Past Participle
Usage:
Express the idea that something didn’t happen, to express
obligation or criticism.
Examples:
She should have asked you before borrowing your pen.
We should have had a proper discussion before voting.
Shouldn’t Have + Past Participle
Usage:
Unwanted things that happened.
Example:
She shouldn’t have taken the matter too seriously.
You shouldn’t have said things like that to her- it really upset her.

7. Needn’t Have + Past Participle
Usage:
Express that something was done but it wasn’t necessary.
Examples:
He needn’t have been so careful.
I needn’t have knocked at the door since, in this way, I awoke
the baby. (but I knocked)

8. Use must, should/shouldn’t/needn’t + have + the past participle of
the verbs in brackets.
1) She ___________ (refuse) that job offer. It was a good opportunity.
2) I _______ (go) to meet her because her brother came to the airport, too.
3) His mother __________ (be) furious when she found out.
4) It’s no wonder you failed the test. You __________ (learn) more.
5) I _____________ (leave) my keys in the car. I can’t find them
EXERCISE