MODAL VERBS.

MODAL	FUNCTION	Example
CAN (poder-saber)	To show ability	I can play the piano. Can you speak Chinese? Yes, I can / No, I can’t.
	To suggest a possibility or give an option	We can watch a film!
	To ask for or to give permission	Can I borrow your car? Yes, you can, / No, you can’t.
CAN’T (no poder-no saber)	To show lack of ability	He can’t drive.
	To show impossibility	We can’t go out during the quarantine.
COULD (podía-sabía)	To show ability in the past	I could ride a bike when I was five years old.
	To show possibility in the past	Could he see his parents last month?  Yes, he could. /No, he couldn’t.
COULDN’T (no podía-no sabía)	To show lack of ability in the past	My brother couldn’t play the guitar at five.
	To show impossibility in the past	We coulndn’t travel to Germany last year. We had to work.
SHOULD SHOULDN’T (debería-no debería)	To give advice	You should study every day. You shouldn’t smoke.
MUST (deber)	To express obligation	You must obey your parents.
MUSTN’T (no deber)	To express prohibition	They mustn’t feed the monkeys in the zoo.
HAVE  TO (tener que)	To express present obligation	You have to do your homework every day.
	To express past obligation	We had to study a lot when we were young.
DON’T HAVE TO DOESN’T HAVE TO (no es necesario)	To express lack of obligation or necessity	You don’t have to make your bed in a hotel.