1. MODAL VERBS

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

5. 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.

6. HAVE (GOT) TO/
MUST
CAN/COULD/
BE ABLE TO
SHOULD/
OUGHT TOMAY/MIGHT