Modal Verbs for Obligation and Necessity

To say something is necessary or obligatory we used the verbs: must, have to, need to.

Have to, and need to are not modal verbs. We form the questions and negatives with ‘do’ and we need to use the third person forms: has and needs.

The Positive Form

To say something is necessary we use: must, have to, need to.

I must find a new job.

I need to find a new job.

I have to find a new job.

There is a difference between must and have to.

We use must to talk about something we feel is necessary.

For example: I must find a new job because I hate it. (I feel it’s necessary)

We use ‘have to’ to talk about something that is necessary because of external circumstances.

For example: I must find a new job because my company is closing. (I have no choice)

The Negative Form

To say something isn’t necessary, we use: don’t have to and don’t need to.

I don’t have to wear a suit to work.

I don’t need to wear a suit to work.

BE CAREFUL Mustn’t has a different meaning. Mustn’t means something is prohibited.

I mustn’t wear jeans to work. (It is prohibited.)

Past

The past of must and have to is: had to.

For example: I had to wear a suit in my last job.

Click on the links below to learn more about modal verbs

Introduction

Modal Verbs for Ability

Modal Verbs for Prohibition

Modals for Permission

Modals for Offers and Requests

Modals for Suggestions and Advice

Modal Verbs for Prediction

Modals for deduction and supposition – Present

Modals for deduction and supposition – Past

Modal Verbs for Obligation and Necessity

Past Modals