Advanced English Grammar

Modal Verbs of Necessity

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 are have to, have got to, and must.

   Have to,must, and mustn't, are used to talk about a necessity in the present or future.
      He has to attend the meeting tomorrow.
      He must attend the meeting tomorrow.
      He mustn't be late for the meeting.

   Had to refers to a necessity in the past.
      He had to attend the meeting yesterday.

   There IS a difference between must and have to when expressing necessity for yourself or others.
      I must be careful not to upset him.
      They have to be in Charlotte before Thursday.

** NOTE **

We normally use have to for things that happen repeatedly with adverbs of frequency like always, often, and regularly.

      I always have to do the shopping on Saturdays.
      You often have to wait in line at the grocery store.

   Must not, or mustn't, shows that it is important for something NOT to happen or take place.
      You mustn't talk during church service.

   Must not and don't have to mean different things. Must not means that it is important that you don't do something. Don't have to means that it isn't necessary to do, but you can.
      You mustn't give me flowers because I'm allergic.
      You don't 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 often do you have 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 the have 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 football practice.

Modal Verbs of Necessity Exercise

1. You ____ turn in your homework by Thursday.
2. Did she ____ go to school last week?
3. I ____ go with you tomorrow. I have no choice.
4. They ____ sell their car for less than what they paid for it.
5. You may ____ read it after all.
6. You ____ be late for school tomorrow, we are having a test.
7. She ___ give the names of the people she was with last night.
8. "I ____ drive until I'm 18," he said.
9. You do ____ come with us if you don't want to come.
10. Mari will ____ take the bus in the morning. I'm leaving early.

For more information concerning the modal verbs of necessity click on the preceding link.

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