Modal verbs are incomplete verbs that do not have all tenses and are used with other verbs to complete their meaning. They are not conjugated for third person singular present tense and are followed by an infinitive without "to" in most cases. Modal verbs do not require an auxiliary verb in questions or negatives. There are different modal verbs that express ideas like ability, permission, obligation, advice, offers, and past possibilities or necessities. Modal perfect tenses are formed with a modal verb plus "have" and the past participle to refer to past actions, and are used to express conclusions, suppositions, abilities, criticisms and regrets about past events.

1. MODAL VERBS
BACHILLERATO

2. Characteristics
 They are INCOMPLETE VERBS. They
don’t have all the tenses. There is not past
participle, so there is not passive. They use
other verbs to complete the tenses.
- CAN is completed with BE ABLE TO
“They can play the piano.”
“They will be able to play the piano in the future.”
- MUST is completed with HAVE TO
“You must come early.”
“You had to come early yesterday.”

3.  They don’t have –s in third person singular of
the present simple
“ He can open the door”
“ She must come early”

4.  They are followed by an infinitive without 'to' in
most cases.
BUT:
NEED takes 'to' when expressing absence of
obligation in the negative:
You do not need to stay if you don't want to.
OUGHT TO is a special case and you must learn
it like that. It expresses convenience.
Ex: You ought to study more more if you want to
pass the exam.

5.  They don’t need auxiliary verb in the
interrogative or negative form
“ Can I help you?”
“ We shouldn’t go to the toilet”

6. PROBABILITY/ OBLIGATION/
POSSIBILITY ABILITY PERMISSION ADVICE OFFERS
CAN I can play the piano Can I go out
tonight?
CAN’T She can’t be his mum. I can’t speak Can I borrow the
She ‘s too young German car? No, I can’t.
MIGHT It might rain tomorrow
MAY NOT If the bus doesn’t arrive
MIGHT NOT soon, we may not see
the start of the film
COULD It could rin tomorrow I could already read Could I see your
when I was two passport please, sir?
MAY It may rain tomoroww May I leave the
table?
MUST She must be his sister You must leave
because they look alike. before the clock
strikes twelve.
HAVE TO I have to study
tonight.
SHOULD / You should see it.
OUGHT TO It’s excellent.
HAD You had better
BETTER sleep more.
WOULD Would you like a
drink?

7. MODALES PERFECTOS
 Son modales que se refieren siempre a acciones
ocurridas en el pasado.
 FORMACIÓN:
MODAL + HAVE + PARTICIPIO PASADO
Ejemplos:
It must have been a difficult decision
They should have invited her to their wedding

8. MODAL PERFECT USES EXAMPLES
MUST HAVE + P.P. Conclusión lógica sobre un Linda has arrived late. She must
hecho del pasado have been in a traffic jam
MAY / MIGHT HAVE + Una suposición sobre algo She may / might have taken
P.P. pasado the wrong bus.
COULD HAVE + P.P. Habilidad de haber hecho algo You could have asked the
pero finalmente no lo hizo doctor before taking that medicine
COULDN’T HAVE + P.P. Certeza de que algo no pudo He couldn’t have gone to the
haber sucedido concert because he was doing a test
WOULD HAVE + P.P. Quiso haber hecho algo, pero I would have gone to the
no pudo hacerlo por causas party, but I was too busy
externas
SHOULD / OUHT TO Queja de que algo haya ocurrido You should / ought to have
HAVE + P.P. en el pasado o lamento de que warned me earlier
no se haya cumplido lo que
esperábamos
SHOULDN’T HAVE + Crítica sobre un acontecimiento He shouldn’t have forgotten
P.P. pasado que no debería haber about her birthday
ocurrido
NEEDN’T HAVE + P.P. No había necesidad de hacer lo You needn’t have brought
que se hizo en el pasado anything to my party.