The modal verbs of necessity show obligations in the past, present, or future. It
can be a necessary action that was required over and over again, or something that occurred just once.
The modal verbs of necessity arehave
to,must, andmustn't, are used to talk about a
necessity in the present or future. Hehas
to attend the meeting tomorrow. Hemust attend the meeting tomorrow. Hemustn't be late for the meeting.
to refers to a necessity in the past. Hehad
to attend the meeting yesterday.
There IS a difference betweenmust andhave to when expressing necessity for yourself or
others. Imust be careful not to upset him. Theyhave
to be in Charlotte before Thursday.
** NOTE **
We normally usehave
to for things that happen repeatedly with adverbs of frequency
like always, often, and regularly.
I alwayshave to do the shopping on Saturdays. You oftenhave to wait in line at the grocery
not, ormustn't, shows that it is important for something
NOT to happen or take place. Youmustn't talk during church service.
not anddon't have
to mean different things. Must not means that it is important that
youdon't do something. Don't
have to means that it isn't necessary to do, but you can. Youmustn't give me flowers because I'm
have to give me flowers but you can if you like.
** NOTE **
Must is only used in the present or future... NEVER for necessities in the past. Also, we use
the auxilary verb 'do' for questions with the 'have to' modal. How oftendo youhave
to buy milk for your children?
Must is never used with other modals, the 'ing' form, the full infinitive 'to' form, or a past
participle. These all require thehave to form. They may have to be sent out of the
classroom. I would have had to go through Leeds to reach
Manchester. He doesn't like to have to do his homework after