1. Modal verbs.
Maria Sivera Penalba
Laura Moratal Valer

2. ·They are invariable, so they only have one form for singular and plural.
·They don’t need “do” to make the negative and interrogative form.
·They are always followed by the infinitive verb (without changes)
·They don’t have infinitive, participle, future, forms in –ing, or compound tenses.
*Be able to and have to don’t share all these rules, but they can be used like modals.

3. CAN
·To express ability in the present. (She can swim very fast)
·To make requests and to ask for permission. (Can I call you tonight?)
·Possibility. (This book can be interesting)
·To make a suggestion. (You can cook the dinner)
CAN’T
·It shares with can all this uses, but in negative, and it also expresses:
-Certainly that something is impossible. (You can’t be 50, you
look much younger)
-Prohibition. (You can’t smoke here.)
BE ABLE TO
·It expresses ability like “can”, but it is used in all the verbal tenses that “can” doesn’t have. (I haven’t been able to visit the museum.)

4. COULD
·It is used to indicate ability in the past.
(He could jump when he was younger.)
·To ask for something more politely than with can.
(Could you give me some information about that?)
·To make suggestion.
(You could go to the dentist.)
·To express a possibility less likely.
(They could come after dinner.)

5. MAY/MIGHT
·They express possibility, the only difference between them is that “might”
Is for a possibility more difficult to get.
(It may rain tomorrow)
(She might come to the party.)
*”May” is also used to ask for something more politely.
(May we meet this week?)
WOULD
·To request or offer something politely.
(Would you give me the pen?)
(Would you like something to eat?)

6. MUST HAVE TO
·Both express obligation and necessity.
·It is used in present.
(You must go to the doctor.)
·It is used by people with authority.
(You must take the pills twice a day.)
·To express certainty that something is true.
(She has passed the exam. She must be very happy)
·It is used in the other tenses.
(You only had to buy the milk.)
·Everybody uses it to say what they have to do.
(I have to take the pills twice a day.)

7. MUSTN’T/DON’T HAVE TO
· Mustn’t: it expresses prohibition. (You mustn’t drink alcohol if you’re going to drive)
·Don’t have to: lack of obligation, “no tener qué o porqué”. (I don’t have to get up early tomorrow.)
NEED TO/NEEDN’T
·It’s not a modal, because:
-It needs an s in the third person singular. (She needs to talk to you.)
-It needs “do” in negative and interrogative form. (Do you need something?)
·However, “needn’t” is a modal, that is used just in negative to indicate that there isn’t obligation or necessity to do something. (Igual que “don’t have to”) (She needn’t come= No es necesario que venga)

8. SHOULD/OUGHT TO
·Both expresses advice and opinion, but should is used more frequently.
(You should/ought to get on well with your sister.)
MODAL+HAVE+PARTICIPLE
· This structure is used to form the perfect modals.
·They have the same uses that we have explained, but in the past.
(She is sad. She must have failed the exam.)
(You needn’t have told her that, she is crying.)