Should, must, and have to are used to express different levels of obligation or necessity. "Should" indicates something is a good idea but is not mandatory. "Must" and "have to" express stronger obligations that something is required to be done. "Must" is used for present and future obligations while "have to" can also refer to past obligations.

1.  Should
 Must
 Have to

2. Used to give advice. It indicates that something is
good and therefore should be done. It is a
recommendation, not an obligation.
Se utiliza para dar consejos. Se indica que algo
es bueno y por lo tanto se debería hacer. Es una
recomendación, no una obligación.
Should

3. Should
Shouldn´t

4. Se utiliza en pasado, presente
y futuro
Should + sujeto...?

5. Must / Have to…
Expressing an obligation to do something.
Expresan una obligación, algo que hay que hacer.

8. Must / Have to…
"Must" se utiliza con el tiempo presente y futuro
"Have to" con pasado, presente y futuro
Pasado Had to
Presente Have to Must
Futuro Will have to Must

9. Must + sujeto + verbo principal ?
Do + sujeto + have to + verbo principal ?

10. "Mustn't": no se debe hacer algo
"Don't have to": no es necesario hacer
algo

11. 1.- You ________ visit Paris. What a beautiful city!
2.- You ________ come with us to the cinema; the film we are
going to see is marvellous
3.- Jane, you ________ rest; you look very tired
4.- I ________ go to the bank to get some money
5.- I ________ leave immediately; it is very late and tomorrow I
have to get up early
should
should
should
have to
have to

12. 6. If I want to buy a new house I ________ get a mortgage
7.- If you want to watch TV, first you ________ finish your
homework
8.- You will have exams in two weeks. You ________ study
harder (obligation)
9.- You ________ leave this place immediately
10.- The doctor is very worried about my dad and has told him
that he ________ work less
have to
must
must
must
has to