Modal Verbs of Obligation

Exercises

Explanation

The most common verbs used for expressing obligation are must, should, and have to, but need to and ought to also appear in many real-life contexts.

1. Should – gentle advice or recommendation

Should is used to give suggestions in a polite, non-forceful way. It tells someone what is a good idea, but the person is not required to follow the advice.

Examples:

• You should take regular breaks if you work on the computer for a long time.

• They should listen carefully before making a decision.

Structure:

• Affirmative: subject + should + verb

• Negative: subject + should not (shouldn’t) + verb

• Questions: Should + subject + verb?

This modal is ideal for offering friendly guidance without sounding strict.

2. Must – strong obligation or personal necessity

Must expresses a strong feeling of obligation. The need usually comes from the speaker’s personal judgment, feelings, or sense of responsibility. It can also be used to give firm, emotional advice.

Examples:

• I must organise my notes today; they are completely messy.

• You must visit the new museum—it’s absolutely worth it.

In the negative form, must not (mustn’t) means something is not allowed or is strictly forbidden.

Examples:

• You mustn’t enter this area without permission.

• Visitors mustn’t touch the artworks in the gallery.

Structure:

• Affirmative: subject + must + verb

• Negative: subject + must not + verb

• Questions: Must + subject + verb?

3. Have to – external rules or requirements

While must often comes from the speaker’s own feelings, have to describes an obligation created by rules, laws, schedules, or other people. The duty is external—not a personal decision.

Examples:

• All passengers have to show their tickets before boarding.

• Mark had to stay for a meeting because his manager requested it.

Important: Don’t have to means there is no obligation. The action is optional—you can do it if you want, but it’s not required.

Examples:

• You don’t have to bring snacks; we already have plenty.

• She doesn’t have to work tomorrow, so she can relax.

Structure:

• I/you/we/they: have to / don’t have to

• He/she/it: has to / doesn’t have to

• Questions: Do/Does + subject + have to + verb?

4. Need to – necessity based on the situation

Need to expresses a practical or logical necessity. It often describes something that is important because of the current circumstances—not because of rules or strong obligation.

Examples:

• We need to charge the camera before the trip.

• She needs to finish the form to complete her registration.

Forms:

• need to / don’t need to

• needs to / doesn’t need to

• Do/Does + subject + need to…?

It is more neutral and less forceful than must or have to.

5. Ought to – moral duty or formal advice

Ought to expresses moral or social responsibility. It is similar in meaning to should, but it sounds more formal and is less common in everyday speech.

Examples:

• You ought to be more patient with younger students.

• People ought to recycle more to help the environment.

Structure:

• Affirmative: subject + ought to + verb

• Negative: subject + ought not to + verb

• Questions: Ought + subject + to + verb?

Although grammatically correct, ought to is used less frequently today and is often replaced by should.

6. Quick Comparison Table

Mastering modal verbs of obligation allows you to communicate clearly about rules, expectations, responsibilities, and advice. Whether you are explaining school rules, giving suggestions, or describing what needs to be done, these forms are essential in both spoken and written English.