1. MODALMODAL
VERBSVERBS
INTRODUCTION TOINTRODUCTION TO
© 2011 Beni Suárez Prado

2. General rules
They help to
express different
meanings:
ABILITY, ADVICE,
OBLIGATION, OR
POSSIBILITY
They do not take -S
for 3rd person
( except HAVE TO)
They lack most
tenses and forms
They are followed
by infinitive
without TO
(except HAVE TO
and OUGHT TO)

3. MOST COMMON
MODAL VERBS
CAN
COULD
HAVE
TO
MUST
MIGHT/
MAY
SHOULD/
OUGHT TO

4. ABILITY
 It is expressed with CAN (present) and COULD (past)
- I can speak English and French.
- When my father was young he could run 10 km in 15 minutes.
 The negative is formed by adding NOT to the modal verb
- He can’t run for long because he suffers from asthma.
- There were lots of people at the concert, so we couldn’t move.
 Questions are made by inverting the SUBJECT and VERB
- How long can you resist under the water without breathing?
- Could you read properly when you were five years old?
 BE ABLE TO is used for the other tenses
- I have been able to drive since I was seventeen.
- She will be able to go on working when her computer is fixed.

5. OBLIGATION
 IN AFFIRMATIVE it is expressed with MUST and HAVE TO
- Students must be in the classroom before the teacher arrives
- My friend has to wear uniform at her school.
 IN NEGATIVE they have different meanings
MUST expresses OBLIGATION/ PROHIBITION (We are obliged not to do sthg)
- We mustn’t enter while they are playing.
HAVE TO expresses NO OBLIGATION (absence of obligation/ we are not
abliged to do sthg)
- You don’t have to do exercise 3 if you don’t want to.
(Difference)

6. Some practice:
CAN, COULD, CAN’T, COULDN’T
Exercise 1 Exercise 2
MUST, HAVE TO, MUSTN’T, DON’T HAVE TO
Exercise 3 ( must, have to)
Exercise 1 (must) Exercise 2 (have to)
Exercise 4 (mustn’t)
Exercise 5 (mustn’t, don’t have to)
Exercise 6 (must, have to, mustn’t, don’t have to)

7. POSSIBILITY and CERTAINTY
MUST
CAN’T
COULD
MAY
MIGHT
We are CERTAIN that something it’s true
DOUBT
Sophie must be at work, it’s ten o’clock and
she works from 8 to 2 pm
I haven’t got any homework, I could go to
the beach this afternoon
I must help my mum, afterwards, I may go to
the beach
I might go to the beach, but I’m not sure
because I’m really busy today.
Sophie can’t be at work, it’s half past three.
We are CERTAIN that something it’s NOT true

8. ADVICE
We can express advice with the modal verbs SHOULD and OUGHT TO
You should study harder if you don’t want to be studying all summer
We ought to hurry up, the film starts in ten minutes and we are still
at home
We can also show advice with the expression “HAD BETTER”
You’d better stay at home; you’ve got a terrible cold and it’s raining
cats and dogs outside

9. Some practice:
CAN’T and MUST
COULD, MAY, MIGHT

10. MODALS + PERFECT INFINITIVE
( HAVE + PAST PARTICIPLE)
COULD
MAY HAVE + past participle
MIGHT
MUST HAVE + past participle
Speculations about the past
“ He could/may/ might have
gone home”
COULD HAVE + past participle
Past ability when the action wasn’t
performed
“ I could have lent you the money”
Deduction about a past action
“ He must have taken sleeping pills”
COULDN’T HAVE + past
participle
Certainty that something didn’t
happen
“ She couldn’t have left her baby at
home”
NEEDN’T HAVE + past
participle
An unnecessary past action
“ He needn’t have cooked dinner”

11. SHOULD HAVE + past participle
Obligation which was not fulfilled and we are sorry it didn’t happen
“ We should have told him it was wet”
Assumption about a past action
“The letter should have arrived by now”
SHOULDN’T HAVE + past participle
It shows disagreement or criticism with a past action
“ We shouldn’t have spent all our money in that house”