MODAL VERBS

AND MODAL PERFECT

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CHARACTERISTICS

• They don’t have a different form for 3rd person singular in the present simple tense.
• They’re followed by a bare infinitive (=infinitive without TO).
• They don’t take an auxiliary verb to make the negative or interrogative . NOT follows the modal verb in negative sentences and the questions are made with inversion, placing the modal verb at the beginning.
• They don’t have -ing form or past participle, and they are not used in future tenses.

* HAVE TO is an exception. It is a semi-modal verb.

USE

They convey different meanings:

• permission
• prohibition
• obligation
• lack of obligation
• advice and opinion
• ability
• possibility

PERMISSION

• Can
• Could

++ May

+++ Might

They indicate formality (might being the most formal).

Can I go to the toilet, please? May I open the door, please?

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PROHIBITION & LACK OF OBLIGATION

Mustn’t express prohibition while don’t have to refers to an action which is not necessary.

You mustn’t park here. It’s a bus stop.

You don't have to bring your books tomorrow. We’re going on a school trip.

OBLIGATION

• Must
• Have to

We use have to to talk about official or external rules. At our school, we have to wear school uniforms.

We use must to emphasize that an action is very important. You must arrive at 8 p.m or you won’t catch the bus.

* Must can only be used to refer to present or future situations.

ABILITY

Can I can ride a bike.

Could (past ability) I couldn’t ride a bike when I was 6.

We use be able to to talk about someone’s ability in all the tenses.

I will be able to speak French by the end of the year.

My friend wasn’t able to speak French last year.

POSSIBILITY & CERTAINTY

• Must indicates certainty or that the speaker is sure about something: John must be at home because his car is in the garage.
• May and might express that something is possible or that the speaker is uncertain (may indicates that the speaker sees the situation more possible or certain) : You may/might pass this subject.
• May not and might not express uncertainty: I may not have time to finish the book tonight.
• Could expresses uncertainty: Peter is late. He could be stuck in the traffic.
• Can’t means that the speaker knows that something is impossible: Mary can’t be in London! I’ve just seen her!

ADVICE & OPINION

• Should
• Shouldn’t
• Ought to
• Ought not to
• Had better

You should go to the doctor to have your arm checked. / You ought to go to the doctor to have your arm checked./ You had better go to the doctor to have your arm checked.

Your shouldn’t tell him the bad news right now. / You ought not to tell him the bad news right now. / I don’t think you should tell him the bad news right now.

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MODAL PERFECT VERBS

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FORM

Modal perfects are followed by the infinitive have and a past participle.

MODAL VERB + HAVE + PAST PARTICIPLE

USE

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We use modal perfect forms when we refer to situations of the past.

REGRET & COMPLAINT

We use shouldn’t have to regret something that happened in the past or to complain about a past situation.

You shouldn’t have told Peter about his surprise birthday party!

We use should have and ought to have to express a criticism about something that wasn’t done in the past.

You should have gone to the doctor earlier.

ABSENCE OF NECESSITY

We use needn’t have to express that there was no need to do something but it was done anyway.

You needn’t have come so early today.

POSSIBILITY

We use could have to indicate a past possibility, that is, to express that something was possible in the past but it didn’t happen.

Mike could have been a good actor, but he forgot to send his application form to the Arts school.

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UNCERTAINTY

We use may have and might have to express that we think something has happened but we are not sure.

Kate is not here yet. She may/might have missed the bus.

IMPOSSIBILITY

We use would have to express something we wanted to do differently in the past but we couldn’t.

I would have gone to see the match, but I had to work.

CERTAINTY

We use can’t have to express the certainty that something has not happened.

Peter can’t have eaten all the cake. It must be somewhere.

We use must have to express the certainty that something has happened.

It must have rained a lot here. Look at the level of the river.