The four most common modal verbs of obligations are must, have to, should, and ought to. We use these modal verbs in any form for rules, laws, strong advice, and warm invitations.
Learn the complete definition and examples of modal verbs of obligations. Then, answer the worksheet I whipped up and provided to test your understanding.
What Are the Modal Verbs of Obligation?
In English grammar, a modal verb is a type of auxiliary verb that indicates a specific modality. These are single-word verbs like should, must, shall, can, and could.
Modal verbs of obligation indicate obligation. This type of verb accompanies the base form of the main verb or the bare infinitive form.
There are two main types of modal verbs of obligation:
- Modal verbs that show a firm obligation (must, have to)
- Modal verbs that show recommendation or moral obligation (should, ought to)
We can express modals in passive or active form. We can also use some in negative forms, perfect forms, and closed question forms. For example:
- Active form: You should read more grammar books to learn English.
- Negative form: You should not accessorize your school uniform.
- Question form: Should I stop smoking?
Modals of Obligation
Let’s look at the different modal verbs of obligation in the English language.
Use must when discussing obligations. It is typically used by a person of strong obligation. The correct form is subject + must + main verb or subject + must not + main verb for the negative form. Must not has no question form or past tense form.
Here are some sentence examples.
- You must go to the office early tomorrow.
- Everyone must not talk loudly.
Must can also indicate warm invitations. Here are some examples.
- You must come to our dinner tomorrow.
- You must join us for a celebration!
You can also express this modal of obligation in its present perfect form using must have or must not have. For example:
- You must have brought your assignment if you wanted to pass the subject.
Must have done is a rare modal verb of deduction or speculation. It is not a modal verb of obligation in the past.
Have to is the same as must, except it expresses external obligation. That means we use have to for rules, laws, and other external obligations. The negative form is don’t have to, which indicates an absence of obligation or negative obligation.
Like other modals, we use have to with a normal verb in its base form. For example:
- You have to clean your room. Mom told you to do it.
- She has to obey the school rules.
- You don’t have to bring the documents if your employer doesn’t require them.
We can also express have to in past form, which is had to or didn’t have to. For example:
- All you had to do was pick her up, but you didn’t.
Its other conjugations are has/have had to, has/have not had to, will have to, and will not have to.
Have got to is a British version of have to, which is stronger than have to. Its negative form is haven’t got to. For example:
- You’ve got to squeeze the ball harder.
- You’ve got to ride the car.
- We haven’t got to pay for the ride.
We can also use got to, gotta, and have got to in informal contexts, usually in the present tense. For example:
Need to implies strong recommendation. Its negative form is don’t need to or needn’t in informal situations. Remember that needn’t does not require a to after it. For example:
- You need to wear red.
- You don’t need to worry about me.
- You need not/needn’t find me.
Unlike must and have to, should expresses weak obligation. This modal verb can also be used to give advice. Its negative form is shouldn’t or should not.
- You should bring your gym uniform to school tomorrow.
- She shouldn’t leave the television on when no one is at home.
- I should not eat too many sweets. It’s terrible for my health.
The present perfect form of should is should have or shouldn’t have. For example:
- You should have passed by my house when you visited the city.
Ought to also expresses weak obligation. Its negative form is ought not to or oughtn’t to when contracted. For example:
- You ought to listen carefully to my story.
- Kelly ought to go by herself to the library.
- They oughtn’t to have let that happen.
The present perfect form of ought to is ought to have or ought not to have. For example:
- Her brother ought to have listened to their warnings.
Modal Verbs Summary
This guide has shown you the meaning and types of modal verbs of obligations. Remember that modal verbs are auxiliary verbs paired with a main verb to indicate modality.
We use modal verbs of obligation in any form for suggestions, obligations, necessity, and warm invitations. The four most common examples are must, should, have to, and ought to.