English Teaching

Modal Verbs: Can, Could, Should, Must โ€” The Complete Guide

๐ŸŽฏ A2โ€“B1
โฑ๏ธ 5 min

๐Ÿ’ฌ From the classroom: A student once wrote “You must to go now.” The to after modal verbs is one of the most common errors at A2โ€“B1. You can fix it in one rule.

Modal Verbs โ€” The Golden Rule

Modal verb + base infinitive (NO “to”)  โ†’  You must go. / She can swim.
Modal Use Example
can ability / permission She can speak four languages.
could past ability / polite request Could you help me, please?
should advice You should sleep more.
must strong obligation (internal) I must call her today.
have to obligation (external rule) You have to wear a mask here.
might / may possibility It might rain later.

๐ŸŽฏ Quick Practice โ€” Fix the Mistake or Choose the Right Modal

  1. You must to ___ finish before 5pm.
  2. She ___ (ability) play the piano when she was 5.
  3. “I have a headache.” “You ___ take a painkiller.”
  4. I’m not sure โ€” it ___ be true or it ___ not.
Reveal Answers โ–ผ
  1. must finish
  2. could
  3. should
  4. might / might not

โœ… Takeaway: Modal + base verb. No “to” after can/could/should/must/might. “Have to” is the exception โ€” but it is not a true modal.


Independent project; not affiliated with, endorsed by, or accredited by Cambridge University Press & Assessment. Confers no qualification.