English Grammar Lab

← B1

Must, have to and should

You will be able to Express obligation, necessity and advice with modal forms.

Explanation

Must and have to express obligation or necessity. Should expresses advice or recommendation.

Examples

Detailed course

Understand the grammar point

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Detailed explanation

This lesson focuses on must, have to and should. The structure helps learners organise connected speech and writing, and it should always be interpreted as part of a complete message rather than as an isolated formula. Before selecting a form, identify the subject, time reference, clause relationship, and the information that receives emphasis.

Formation is central. Use must or have to before the base verb for obligation and necessity, and should before the base verb for advice. Must not prohibits an action, while do not have to means it is unnecessary. Build the sentence in stages: identify the grammatical subject, choose the auxiliary or main verb form, and complete the clause in normal English word order. In negatives and questions, check whether the structure supplies its own auxiliary or requires another one.

The pattern can help users explain reasons and results, report experience and information, and choose between related grammar patterns. These purposes may overlap, so context decides which interpretation is natural. Time expressions, determiners, linking words, and punctuation often provide evidence for the correct choice.

A useful contrast prevents overgeneralisation. Must often reflects the speaker’s authority or a formal rule, while have to commonly describes an external requirement. Ask how the nearest alternative would change time, certainty, focus, politeness, or register. A grammatically possible sentence may still communicate the wrong relationship if that contrast is ignored.

The guided examples are complete messages. Notice how the target structure agrees with its subject and how the surrounding vocabulary makes the intended meaning clear. When producing a new example, preserve the relationship between form and meaning while changing the people, place, and lexical details.

A reliable self-check is to paraphrase the sentence in simpler language. If the paraphrase changes the time relationship, degree of certainty, or focus, review the original form. Compare the sentence with the common mistakes and explain why the corrected version is preferable.

In connected speech and writing, the structure also contributes to cohesion. It guides the reader through background information, main events, causes, qualifications, and results. Clause order and connector choice can therefore affect interpretation even when every individual word is correct.

How to form it

Use must or have to before the base verb for obligation and necessity, and should before the base verb for advice. Must not prohibits an action, while do not have to means it is unnecessary.

Use the structure to organise connected speech and writing.

Use the structure to explain reasons and results.

Use the structure to report experience and information.

Use the structure to choose between related grammar patterns.

Must often reflects the speaker’s authority or a formal rule, while have to commonly describes an external requirement.

Guided examples

All visitors must wear an identification badge.

Must expresses a strong obligation, followed directly by the base verb wear.

Staff members have to complete a safety form.

Have to expresses a necessity that comes from a rule outside the speaker.

You should bring a reusable bottle to the event.

Should gives advice, not a strict obligation, before the base verb bring.

Guests must not enter the storage area.

Must not prohibits an action completely, unlike must, which requires one.

Children do not have to pay for the workshop.

Do not have to shows the action is unnecessary, not forbidden.

The organisers had to change the entrance yesterday.

Had to is the past form of have to, used here for a past necessity.

Common mistakes

Not: All visitors must to wear an identification badge.

Use: All visitors must wear an identification badge.

Must is followed directly by the base verb, without to.

Not: Staff members has to complete a safety form.

Use: Staff members have to complete a safety form.

Members is plural, so it needs have to, not has to.

Not: You must bring a reusable bottle to the event.

Use: You should bring a reusable bottle to the event.

This is friendly advice, not a strict rule, so should fits better than must.

Not: Guests do not have to enter the storage area.

Use: Guests must not enter the storage area.

Do not have to means the action is unnecessary; to forbid it, the sentence needs must not.

Before you practise

  • Identify the communicative purpose.
  • Check the subject and required verb or auxiliary.
  • Confirm the time reference and clause order.
  • Compare the sentence with the nearest alternative.
  • Read the complete sentence and verify the meaning.

Reading text

Rules for the Public Workshop

About 266 words

Maha, the volunteers, and visiting families gathered at the public workshop room to run a craft event safely. The main difficulty was clear: new helpers arrive just before the doors open. They spread tools, glue guns, badges, and safety cards across the table and agreed to work through the facts one by one. Volunteers must check the tools before the doors open. That first detail changed the mood in the room because it gave the group something concrete to discuss. Visitors have to sign in at the front table. After that, the group compared names, times, and places instead of guessing. Children must not touch the hot glue guns. A short disagreement followed, but it helped them notice a missing detail. New helpers should ask questions if they are unsure. When the final note was added, the plan felt realistic and easy to explain. Before they left the public workshop room, the result was clear: everyone follows the plan without stopping the event. Maha, the volunteers, and visiting families return to tools, glue guns, badges, and safety cards because each item helps with the task. The notes show why new helpers arrive just before the doors open. The group checks the time, the place, and the next decision before moving on. No one rushes, because a small error would change the outcome. The work stays connected to the public workshop room, where the problem first became visible. By the end, the result is clear: everyone follows the plan without stopping the event. Later, the written record helps the group explain the decision without adding new claims.

Reading comprehension

  1. Who is involved in the reading?

    Show answer

    Maha, the volunteers, and visiting families

  2. Where does the reading take place?

    Show answer

    the public workshop room

  3. What task are the people trying to complete?

    Show answer

    run a craft event safely

  4. What problem makes the task less simple?

    Show answer

    new helpers arrive just before the doors open

  5. How does the reading end?

    Show answer

    everyone follows the plan without stopping the event

Grammar in the text

  1. Volunteers must check the tools before the doors open.

    Must expresses a strong obligation before the base verb check.

  2. Visitors have to sign in at the front table.

    Have to shows a necessity that comes from the workshop’s own rules.

  3. Children must not touch the hot glue guns.

    Must not forbids the action completely.

  4. New helpers should ask questions if they are unsure.

    Should gives advice rather than a strict rule.

Key point

Use this pattern when the meaning needs it in the reading: modal or have to + base verb. In short, must, have to, must not, and should express rules and advice. Example: "Volunteers must check the tools before the doors open."

Practice

  1. Complete the sentence from the same situation: "Volunteers must ____ the tools before the doors open."

    Show answer

    Volunteers must check the tools before the doors open.

  2. Complete the sentence from the same situation: "Visitors ____ sign in at the front table."

    Show answer

    Visitors have to sign in at the front table.

  3. Complete the sentence from the same situation: "Children ____ touch the hot glue guns."

    Show answer

    Children must not touch the hot glue guns.

  4. Complete the sentence from the same situation: "New helpers should ask questions if they ____ unsure."

    Show answer

    New helpers should ask questions if they are unsure.

Listening practice

Watch a TEDx talk

“10 ways to have a better conversation” — Celeste Headlee (TED). Listen for clear, natural English and pick up new vocabulary while you review this grammar point.

Check your understanding

Which of these is one of Celeste Headlee's rules for a better conversation?

Check your understanding

What does Headlee say is the single most important skill for having a good conversation?

Practice

Choose the correct answer. You ___ wear a seat belt in a car.

Practice

Choose the correct answer. I ___ get up early because work starts at seven.

Practice

Choose the correct answer. You look tired. You ___ rest.

Written practice

Produce the answer yourself. Capitalisation and final punctuation do not affect validation, but the grammar and word order must be correct.

Sentence correction

Written practice

Correct the sentence.

You should to get more sleep.