Simple Modal Verbs
Form and Uses
General aspects as regards FORM
All modal verbs are followed by another verb in its base form.
They have no –s /-es in 3rd Person singular, except for HAVE
TO: He has to do an exam and NEED: He needs to buy some petrol.
The modal verb is also auxiliary verb: Can I go to the toilets?
Should I speak to him? Except for HAVE TO: Does he have to do an
exam? and NEED TO: Does he need to buy any food?
Main USES of modal verbs
• We will deal with modal verbs grouped according to the concept
they mean: ability, possibility, obligation, probability and
deduction, permission, requests, offers, suggestions.
• Remeber that one modal verb can express different concepts:
I can dance (Ability)
You can come with us (Permission / Possibility)
• Likewise, one concept can be expressed by different modal verbs:
You should / ought to apologise (Advice)
ABILITY: can / could / be able to
CAN: present events
BE ABLE TO: all tenses
She can speak several languages She is able to speak several
She was able to speak French
better before.
She will be able to speak English
better after several classes.
She has been able to speak
French since she was a child.
- Specific ability in a specific past
COULD: past events
Although she was very nervous,
When she was living in Paris, she she was able to come out and
could speak French better than
speak in front of the audience.
OBLIGATION: must / have to
MUST: the order comes from the
speaker itself. Only present or future
You must be back soon this evening.
We’ve got guests for dinner.
- Moral obligation. The duty comes
from the speaker.
I must study more for the next term. I
don’t want to fail this year.
HAVE TO: the order comes from an
external authority. All tenses and times.
I can’t stay longer. I have to come back
home. We’ve got some guests today.
- Imposed obligation. We are obliged to
do it.
I have to study more or my parents
won’t let me go to a journey next
I have to pay my road taxes today.
HAVE TO can be used in the rest of tenses.
HAD TO is the past form of MUST.
They will have to stay here longer if they don’t finish their work in time.
We have had to delay the appointment for tomorrow.
I had to study harder to pass my exams in the last term.
Other uses related to Obligation
NECESSITY: have to / need to
There is no moral obligation implied.
I have to buy some more bread for tonight’s dinner.
I need to pass all my exams to study at university.
PROHIBITION: mustn’t, can’t
You mustn’t/can’t speak to each other in an exam.
LACK OF OBLIGATION: don’t have to
You don’t have to do the exam if you don’t feel well. You can do it
another day.
I don’t have to get up early tomorrow. It’s a holiday.
FACTUAL POSSIBILITY: may / might / could (only in affirmative/interrogative)
We give one possibility of something to happen. It is one option among several.
They only express Present or Future
He may/might/could come to the party this evening.
(Perhaps, he will come to the party)
He may/might not come to the party this evening.
(Perhaps, he will not come)
They may/might/could be playing in the garden.
(Maybe, they are playing in the garden now)
Spanish translation (Puede que... / Podría ser que…)
When telling past events use might:
Yesteday, I stayed home all day because my mother might phone me, but she didn’t.
(Its was possible that my mother would phone me yesterday)
THEORETICAL POSSIBILITY: can (present) / could (past)
We say that something is possible to happen because there are the
means or appropriate characteristics to be so.
Turtles can live for many years.
We can use that computer again. It already works.
He seems to be unpleasant but he can be very funny at times.
You can be here on time if you wish. You’ve got a fast car.
Spanish translation ( El verbo poder conjugado: puede, puedo,
He couldn’t come to the party yesterday. He was too busy.
That door can’t be locked. It is broken.
Factual and Theoretical Possibility
It may be rainy in Praha. (Possibly, it is rainy in Praha now )
It can be rainy in Praha. ( It is usually rainy in Praha )
He may come to the party. (Perhaps, he will come to the party)
He can come to the party. (It is possible for him to come to the party.
There is no trouble)
PROBABILITY / DEDUCTION: should / ought to / must
We say that something is probable to happen because there is a logical
My father should be in his office right now. He leaves work later. (I suppose my
father is in the office now because of the time)
They ought to win the match tomorrow. The other team is much worse. They
shouldn’t fail. (I expect they will win)
To express the highest level of probability, we use MUST.
He must play the piano quite well. He has been playing it since he was six.
(I am sure he plays the piano quite well)
With SHOULD / OUGHT TO, we can also express surprise because some
facts are different from expected.
He shouldn’t be home at this time. Why is he there?
He should be here now. Where is he?
It is the only negative form for MUST when expressing deduction
My father can’t be working in the office now. He leaves work earlier
He can’t know anything about playing the piano. He has never done it.
They may be studying. (Maybe, they are stduying but we are not sure)
(A lo mejor están estudiando)
They should be studying. They went to the library. (It is what we
suppose or expect)
(Según lo razono, deberían estar estudiando)
They must be studying in the library. I’ve just seen them. (I am sure
they are studying)
(Deben de estar estudiando con toda seguridad)
ADVICE: should / ought to / must / can / could
SHOULD / OUGHT TO: they may imply some moral obligation or
necessity from the listener. We think of it as the only good piece of
In my opinion, you should visit the doctor. You don’t look well.
You shouldn’t talk so loud. Your throat will hurt.
To express strong advice, we use MUST. (More colloquial).
The concert is brilliant! You must go.
NOTE: It is not an obligation.
CAN / COULD: they don’t imply any moral issue but a suggestion that
you give among other possible ones.
If you need some money, you can ask for a loan in a bank or you even
could borrow some from your parents or a close friend.
Asking for permission: may / can / might / could
May/Can/Might/Could I use your telephone, please? Yes, sure!
Giving permission: may / can
Yes, you may/can go to the toilets.
REQUESTS: can / could / will / would you mind
Can / could / will you borrow this book for me?
Would you mind borrowing this book for me? (Pay attention to the –ing form of the main
OFFERS: can / could / may / shall / will
Can / could /may /shall I help you?
I can / will help you with your homework.
SUGGESTIONS: shall we…? / can / could
Shall we go to a different place for a cup?
We can go to the theatre. There is a good play on.

Simple Modal Verbs