Want to sound more natural in English? Master four small but powerful words: can, could, should, must. These “modal verbs” help you talk about ability, permission, advice, and rules in everyday life—at school, at work, and with friends. In this lesson, you’ll learn simple patterns, common meanings, and polite ways to ask for help, plus you’ll practice right away with short exercises.

What are modal verbs?

Modal verbs are special helping verbs. They change the meaning of the main verb. Today’s modals: can, could, should, must.

Can: ability and permission

Use can to say what is possible for you and others, and to ask for or give permission.

Common uses:

• Ability: I can drive. She can play the piano.
• Permission: Can I sit here? You can use my pen.

She ride a bike.

Vocab that often appears with can

Could: past ability and polite requests

Use could for ability in the past and to make very polite requests. It’s softer than can.

Common uses:

• Past ability: When I was a child, I could swim.
• Polite request: Could you pass the salt, please?
• Possibility (less certain): It could rain later.

you open the window, please?

Should: advice and recommendations

Use should to give advice or suggestions. It’s helpful, not a rule.

Common uses:

• Advice: You should sleep earlier.
• Recommendation: You should try the soup—it's delicious.
• Expectation: The train should arrive at 10.

You drink more water.

Must: strong necessity and rules

Use must for strong personal necessity or strict rules. Use mustn’t for prohibition (not allowed).

Common uses:

• Strong necessity: I must finish this tonight.
• Rules: You must show your ID.
• Prohibition: You mustn’t smoke here.

You park here. It’s a private space.

I finish this report today. The boss wants it now.

He must to go. → He must go. After a modal, use the base verb (no "to"). Could you to help me? → Could you help me? No "to" after modals, even in questions. You don’t must bring ID. → You don’t have to bring ID. To say something is not necessary, use "don’t have to," not "don’t must."

Quick practice: choose the right modal

Think about meaning: ability, permission, advice, rule/prohibition, past ability, or polite request.

Forming negatives and questions

• Negatives: add not (often contracted)
  • I cannot (can’t) drive today. She shouldn’t be late. We mustn’t be noisy.
• Questions: modal + subject + base verb
  • Can you come now? Should we call them? Must I sign here?

Cultural notes: sounding natural

• In many English-speaking places (the US, UK, Canada, Australia), Could you…? is a friendly, polite way to ask for help in shops, cafés, and offices. Can you…? is also okay, but sounds a bit more direct.
• Must is strong. In conversation, people often use have to for obligation (You have to wear a helmet), especially in American English. Must is common in written rules and signs.
• For advice, should is softer and more common than must. Saying You must… to a friend can sound too strong unless it’s really necessary.

Summary

• Can = ability/permission now
• Could = past ability; polite request; possibility
• Should = advice/recommendation
• Must = strong necessity/rules; Mustn’t = not allowed

Remember the simple pattern: modal + base verb (no to), no -s, and use contractions in speech (can’t, shouldn’t, mustn’t, couldn’t). Practice a little every day—soon these small words will make your English clearer, more polite, and more confident.

Final encouragement

You’re doing great! Keep noticing modals on signs, in emails, and in conversations. Try using Could you…? at a shop, or give a friendly suggestion with You should…. Small changes make a big difference.