MODAL VERBS: CAN/COULD, MUST,
MAY/MIGHT, SHOULD/OUGHT TO
They are very important in English. They are very often used. They have no meaning
in themselves but they help speakers to express meanings such as: doubt,
obligation, ability, advice, possibility, etc.
I may
(it is not correct unless it is the answer to something previously said)
I may come tomorrow. (speaker is not sure, he expresses doubts)
I can come tomorrow (capacity, possibility) (nothing stops me)
I must come tomorrow (compulsory) (I have an obligation)
I should come tomorrow (advice, suggestion) (speaker thinks it would be a
good idea)
I needn´t come tomorrow. We
have already finished (there is no need
for me to come)
Which are the modal verbs?
Can/could: poder, saber
May/might: quizá, es posible que…
Should/ought to: debería….
Must: deber (obligación) o deber de (suposición)
Needn´t: no necesitar…
Common traits/characteristics:
1) They are always followed by a verb in infinitive without TO: IT MAY TO RAIN
2) They never have –s in 3rd person singular present tense: HE CANS
3) They don´t need auxiliaries in interrogative or negative forms:
Can I help you?
Must you speak so loud?
May I go to the bathroom?
It´s very cold. You shouldn´t go out without a jacket.
You mustn´t be late for class
4) They lack verbal tenses so they need SUBSTITUTES to help them solve this
problem. VERY IMPORTANT: SUBSTITUTES ARE NOT MODAL VERBS.
CAN/COULD :PODER O SABER
CAN: PRESENT TENSE (PRESENT OR FUTURE MEANING)
I can drive (ability, I know how to do something)
I can see you tomorrow if that´s OK with you. (Possibility)
How can I help you? (polite offer in the present)
COULD: PAST and CONDITIONAL TENSE
I couldn´t talk to the teacher yesterday, he was very busy
Could you open the window, please? (polite request)
Could you lend me some money? (polite request)
COULD HAVE+V3: POSSIBILITY IN THE PAST
You could have been killed!!!
She could have passed all her exams if only she had studied a bit more!!
SUBSTITUTE: TO BE ABLE TO
I´d like to be able to swim
I will be able to drive when I am 18
She has been able to change the tire without any help
He was able to drive after two years taking lessons (great effort)
Finally I´m able to fit in this dress after 6 months on a crash diet (great effort)
MAY/MIGHT: PUEDE SER, QUIZÁS, ES POSIBLE
QUE… (uncertainty or possibility, permission)
I may/might see you soon (I´m not sure)
It may/might rain tomorrow (I´m not sure)
May I open the window? (asking for permission= Can I open the window?)
May I go to the toilet? (asking for permission)
May I come in? (asking for permission)
EXPRESSING POSSIBILITY OR UNCERTAINTY IN THE PAST:
Jean may/might have missed the train ( perhaps she did, speaker is not sure)
Tim may/might not have got your letter (perhaps he didn´t; speaker is not sure)
MUST/MUSTN´T/NEEDN´T: DEBES, NO DEBES,
NO NECESITAS
PRESENT OR FUTURE
You must be here at 8 o´clock tomorrow (it is mandatory)
You mustn´t smoke at school (it´s forbidden)
You needn´t bring your books tomorrow, we won´t be using them (there is no need)
SUBSTITUTE: HAVE TO (it is not a modal verb. You have to use auxiliary verbs in
questions and negative sentences) ALL VERBAL TENSES
You have to bring your books tomorrow (it is mandatory) = You must bring
Do you have to bring …..?
You don´t have to bring
Yesterday we had to bring the books
Did we have to bring the books…?
We didn´t have to bring..
Tomorrow I will have to bring the books
 IMPORTANT: You don´t have to bring your books tomorrow=You needn´t
bring your books tomorrow
 IMPORTANT:
NEEDN´T HAVE +V3: I NEEDN´T HAVE BROUGHT THE BOOK TODAY (I BROUGHT IT
BUT IT WASN´T NECESSARY; I MADE A MISTAKE)
DIDN´T NEED TO+INFINITIVE: I DIDN´T NEED TO BRING THE BOOK (I DIDN´T BRING
IT; I LEFT IT AT HOME)
MUST/CAN´T: DEBER DE/NO PUEDE SER
(DEDUCTION)
PRESENT:
Mary: She is not in class today. She must be ill. (I think she is ill)
Peter: She can´t be ill. I saw her this morning on the bus to Madrid.
PAST:
Mary: I must have left my purse in the car. I took it out to pay the toll ( I think I did)
Peter: You can´t have left it there. You paid for the ice-creams 10 minutes ago (I´m
sure you didn´t)
SHOULD/SHOULDN´T/OUGHT TO/OUGHTN´T TO:
PRESENT OR FUTURE
You should phone Peter and make peace with him. (a piece of advice)
You shouldn´t leave everything for the day before the exam (an opinion)
You ought to/should see a doctor if you keep having strong headaches
 HAD BETTER/´D BETTER (STRONG ADVICE)
You´d better stop talking right now!!
You´d better not talk to me like that
PAST
You should have phoned/ought to have Peter as I told you (criticism)
You shouldn´t have left/ought not have left everything for the day before the exam
(criticism)