These verbs cannot be used as lexical (or principal) verbs. Modal Auxiliary verbs are as follows: Ought to, might, need, used to, shall, should, world, may, can, could, will, must.
(a) OUGHT TO: We can use it to denote logical necessity. E.g. you ought to respect your Parent
(b) MAY: It is used to demonstrate or express possibility. Example: I may go to Jos after the conference,
You can use ‘May’ when asking for permission to do something.
E.g. May I meet you today?
May I take your ruler?
May I eat the fruit?
(c) USED TO- It tells about the existence of something in the past. E.g.
* There also used to be some flowers in the school.
– It also shows past habit. E.g.
* She used to smoke
* He use to steal his father’s money.
– It means ‘accustomed to’. Eg. Mr Okoro is used to hard work
(d) SHALL: This is used as part of the future tense (in other words shall is used to express the future) An Example:
I shall attend the meeting
(e) WOULD: This is the past tense of ‘will’
Mr. Adeoye told me he would visit me the next day.
(f) NEED: It is used to show the absence of obligation. An example
* She needs to go away at this material time