Modals I

Have to - Don't have to - Must - Musn't

We have to study for the History exam.

We must revise all the key concepts for the final exam.

We mustn’t use our phones in the Computer Science lab.

We don’t have to memorize all the formulas for Physics.

She has to complete his Biology project by Friday.

They don’t have to write an essay for English class this week.

He mustn’t skip Art class without a valid reason.

Must - Mustn't

• To talk about rules, regulations and obligations that come internally, from ourselves (speakers point of view).
• To talk about prohibitions.

Must + V. Infinitive

Must + NOT + V. Infinitive

Students must read the assigned pages for English Literature.

Have to - Don't have to

• To talk about things which are obligatory or necessary. Described obligations imposed on us by other people.
• To talk about things which are not obligatory or necessary. 

We don’t have to bring our Art supplies today, the teacher is showing a video.

Have to + V. Infinitive

Don't have to + V. Infinitive

1. We ________ bring our Art supplies today—the teacher is showing a video.

2. I ________ finish my Math homework because the teacher said it’s due tomorrow.

3. They ________ attend extra English lessons after school. Their parents signed them up.

4. You ________ do the optional exercises in the Physics workbook.

5. He ________ study for the Geography test because his parents want him to improve his grades.

It's the first week back at school, and Mr. Lewis is explaining the rules to his students.

"Welcome back, everyone! There are a few things you need to remember this term.

First, you all (1) ________ wear your school uniforms every day. It’s part of the school policy.
You (2) ________ be in class by 8:00 a.m. sharp—punctuality is important.
During Science lab, you (3) ________ wear safety goggles at all times for your protection.

Also, you (4) ________ use your phones during lessons—it’s not allowed.
But don’t worry—you (5) ________ bring your own textbooks for Literature; we’ll provide class copies.

Finally, you (6) ________ hand in your homework on time, especially for Math and English."