Modal verbs are helping verbs that provide information about the main verb regarding necessity, possibility, permission, and other meanings. Some common modal verbs are can, could, may, might, should, ought to, had better, must, and have to. Modal verbs are followed by the base form of the main verb. While some modal verbs like must and have to can have similar meanings, they are sometimes used to convey slightly different obligations based on internal or external factors. Other modal verbs like should, ought to, and had better can express varying levels of suggestion, recommendation, or severity in obligations.

1. Modal Verbs
Helping verbs – they give information about the main verb.
• Necessity
• Possibility
• Permission
• Etc.

2.  Can: Natalie can play tennis today. (ability or
permission)
 Could: They could play the guitar.
 (Formal of “can”)
 May: It may be a nice day tomorrow.
(possibility)
 Might: It might be a nice day tomorrow.
(possibility)
Modal + Simple Form

3.  Should: Natalie should go outside.
 Ought to: You ought to tell her how you
feel!
 Had better: They had better be on time.
 Must: He must eat all his food.
 Have to: I really have to study for my
exam.

4.  Similar meaning about obligation
 MUST: Usually used for feelings and
wishes of the speaker.
◦ I must stop smoking. (I want to)
 HAVE TO: Usually obligations that come
from „outside‟
◦ I have to stop smoking (The doctor
ordered me)
Must / Have to?

5.  They have the same meaning in most
situations (suggestion or
recommendation)
 SHOULD: Suggestion or advice about the
best thing for them.
◦ You should tell her how you feel.
 OUGHT TO: Suggesting something they
can‟t avoid or the last option.
◦ You ought to tell her how you feel.
Should / Ought to?

6.  Make suggestions or recommendations
◦ You had better take your umbrella with you
today.
 Warning
◦ You had better be careful with the way you talk
to me in the future!
 Show desperation (hope).
◦ The bus had better arrive on time or I‟ll be late
for work!
Had better!

7.  You should clean your room, it is very
messy.
 You ought to clean your room, your
girlfriend is coming to visit you.
 You had better clean your room, or you
will be grounded!
Levels of severity