Modal verbs- Obligation (Must, have to, mustn't, don't have to, should, ought to, had better, is/ are to)

Hi everybody!! Today I'm going to explain about the modal verbs of obligation. These modal verbs are Must, mustn't, have to, don't have to, should, ought to, had better and is/are to.

1. Must and have to:

•   Must: 

1.      This is to show that something is important or necessary.It refers to something that happens in the present or future.

You must start working harder!

2.      If you must do something in the future.

I must phone my sister.

3.      This is used for emphasis:

I must say, you are looking extremely well.

·         Have to:

       1.      This is when the situation makes something necessary:

  You have to turn left here.

2. Mustn’t and don’t have to:  In negative they are completely different.

·         Mustn’t:  Describes something that is prohibited.

           You mustn’t leave the car in this street.

·         Don’t have to: This describes something that not is necessary.

       

          You don’t leave me alone.

"Must not" suggests that you are prohibited from doing something. "Do not have to" suggests that someone is not required to do something.

3. Should and ought to:  Both can also express something between recommendation and obligation. These modals give an opinion, advice or polite instructions.

I think you should see a doctor.

You ought not to smoke if you are pregnant.

4. Had better: Give an advice about the present or future. This also gives advice about specific situation, not general ones.

           I had better not come.

6. Is/are to: This is used in formal situations.

                 

                      You are not to leave the room.

I hope my lesson of today was useful for you! If you have any question, just ask me!