MODAL VERBS
may/might
must/mustn't
need/needn't
should/ought to
shall/will
be able to
can/could
have to
both is used for giving advice, opinions
should
- express necessity
- lower level than "must"
ought to
- same as "should"
- higher level than "should" but lower level than "must"
- describe the necessity of doing something right in the rules
both is used for describing what might happen but not sure about that
may
- describe something can happen in the present
might
- describe something can happen in the past
- lower level than "may"
both is used for making a decision at the time of speaking
shall
- asking for permission, giving suggestions
- offering to help someone
will
- describing, guessing the thing that will happen
- offering that someone will help
must
- describe necessity of doing something (perceive it yourself)
mustn't
- to say that is strictly banned
- describe probability
- describe possible things can do by trying
"need" is both normal verb and modal verb.
normal verb
needs auxiliaries in negative and question sentences
verbs come after "need" have to be in form "to infinitive"
modal verb
only available in present form
has all the characteristics of a modal verb
needn't
- means "not necessary"
both is used in questions of request, permission
can
- describe the present or future possibility that a person can do something, or an event that may happen
could
- describe the past possibility that a person can do or something, or an event that may happen