6. MUST = Strong Obligation (MUSN’T =
Prohibition)
CAN = Permission (CAN’T= Absence of
Permission)
HAVE TO = Obligation (because I feel that I
need to do it) DON’T HAVE TO = absence of
obligation)
7. 1) Modal verbs are invariable: they have ONE
form for all the 1st, 2nd and 3d form.
That means, you don’t add “S” in the 3d
person
Examples:
You must study. She must study. He must
study
8. 2) Modal verbs don’t have “DO support” in
interrogative and negative sentences
Example:
Must you study? Can I go now?
I mustn’t eat ice cream because I’ve got flu.
I can’t go out because my mom told me to
clean up my room
9. 3) After modal verbs you use INFINITIVE form
of a verb without TO
Examples:
I must sleep well
I can swim
10. 4) Modal verbs don’t have Past Participle
form, Future Tense or ING form
Can – only Can (in Past only could)
Must – only MUST
11. 5) The exception is “HAVE TO”:
A) It has “S” in the 3d form (She has to study
hard)
B) HAVE TO has “Do support”: I don’t have to
study. Do you have to study?
C) HAVE TO has Past Participle and Future
Tense: I had to study hard yesterday. I’ll have
to study hard tomorrow
