Modal verbs have special rules regarding conjugation and usage. They are used to express ability, possibility, deduction, permission and obligation. Modal verbs include can, could, may, might, must, shall, should, ought to, and be able to. They have no inflected forms and are followed by the bare infinitive of other verbs. Modal verbs are used to talk about abilities and skills in the present or past, express possibilities and deductions, and discuss obligations or permissions.

1. MODAL VERBS
- General rules
- Ability
- Possibility and Deduction

2. What is special about modal verbs?
1- Modal verbs have no -s on the third person singular.
- She can play the piano.
- He may come tomorrow.
2- Questions and negatives are made without “do”
- Can your mother drive?
- Should I dress up to go to the party?
- You shouldn’t speak like that
- You cannot smoke at school
3- They are followed by the infinitive without to of other
verbs (except “ought to”)
- She could be in Paris or London or Tokyo - nobody
knows
but - You ought to stop worrying about your weight.

3. 4 - They have no infinitives, past participles or
-ing forms, and other expressions are used
instead.
For example we use “be able to” instead of can
Compare these examples:
- Mary can speak English very well.
- You will be able to drive a car when you are 18.
(infinitive)
- I have never been able to understand my son.
(past participle)
- I love being able to get up late on Sundays. (-ing
forms)

4. EXPRESSING ABILITY: CAN,
COULD, BE ABLE TO
CAN expresses ability to do something.
(saber)
She can skate very well but she can’t swim
(= She knows how to skate but she
doesn’t know how to swim)
Notice this:
*You will be able to speak English fluently
when you go to England.
*Being able to speak several languages is
amazing.

5. COULD.
A) General ability in the past. (sabía)
- My grandfather could speak five languages.
- When Tom was 16, he could run 100 metres in 11
seconds.
But if we refer to a particular situation, we have to use
was/were able to (pudo...)
- The fire spread through the building very quickly but
everyone was able to escape.
- They didn’t want to come with us at first but in the end
we were able to persuade them.
Compare could - be able to:
- Jack was an excellent player. He could beat anybody
but once he had a difficult game against Alf. Alf played
very well but in the end Jack was able to him.

6. Couldn’t is possible in all situations (general
or particular):
- We tried hard but we couldn’t persuade
them to come with us.
- My grandfather couldn’t swim.
Could is used with verbs like “see, hear,
smell, understand”
- Although they were whispering, I could
hear what they said.
- I was a long way from the stage but I could
see it all right.

7. POSSIBILITY AND DEDUCTION
CAN: General possibility. (poder)
- It can be cold in Granada in winter.
- Anybody can make a mistake.
- You can swim because there is an indoor swimming-pool
in our town.
MAY/ MAY NOT: Present of future possibility.
- I may go to aerobics class. (puede que)
- He may start a diet tomorrow.
MIGHT / MIGHT NOT / COULD: Remote possibility in the
present or future. (pudiera ser que)
- She might win the race, but she hasn’t trained hard
enough.
- Are you sure about it?, You could be wrong.
- Look at the sky. It could rain this afternoon.

8. POSSIBILITY IN THE PAST:
May/ might/could have+ past part.
A guess about a past action. We do not know
what actually happened.
Paul is late for work. He may have missed
the bus, he might have overslept or he
could have had an accident.
When you had the ability or possibility of doing
something in the past; but you didn’t do it.
I could have gone to the party but I didn’t
want to

9. LOGICAL DEDUCTION: MUST /
CAN’T
The lights are on. She must be at home.
(affirmative)
The lights are off. She can’t be at home
(negative)
In the past…
Paul didn’t answer my calls. He must have
been out all day.
John can’t have studied hard. He failed the
exam

10. LOGICAL DEDUCTION: MUST /
CAN’T
The lights are on. She must be at home.
(affirmative)
The lights are off. She can’t be at home
(negative)
In the past…
Paul didn’t answer my calls. He must have
been out all day.
John can’t have studied hard. He failed the
exam