🔑 Modal Verbs: Can, Should, Must

Modal verbs are helping verbs that express ability, permission, advice, necessity, and obligation. The verbs can, should, and must are used to express different degrees of necessity or possibility.

✅ 1. CAN – Ability / Permission / Possibility

Can is used to show what someone is able to do, to give or ask for permission, or to express that something is possible.

📌 Uses of "Can":

• Ability: I can swim very fast.
• Permission: Can I use your phone?
• Possibility: It can be cold in December.

🔁 Structure:

• Affirmative: Subject + can + base verb
  Example: She can play the piano.
• Negative: Subject + can’t + base verb
  Example: He can’t drive yet.
• Question: Can + subject + base verb?
  Example: Can you help me?

✅ 2. SHOULD – Advice / Recommendation

Should is used to give advice, make suggestions, or express what is expected to happen or be the right thing to do.

📌 Uses of "Should":

• Advice: You should eat more vegetables.
• Expectation: The train should arrive soon.
• Recommendation: Students should study regularly.

🔁 Structure:

• Affirmative: Subject + should + base verb
  Example: We should leave early.
• Negative: Subject + shouldn’t + base verb
  Example: You shouldn’t eat too much sugar.
• Question: Should + subject + base verb?
  Example: Should I bring my notebook?

✅ 3. MUST – Obligation / Strong Advice / Deduction

Must is used to express strong necessity or obligation, strong advice, or logical deduction.

📌 Uses of "Must":

• Obligation: You must wear a seatbelt.
• Strong Advice: You must see that movie – it’s amazing!
• Deduction: He must be tired after that run.

🔁 Structure:

• Affirmative: Subject + must + base verb
  Example: I must finish my homework.
• Negative: Subject + mustn’t + base verb
  Example: You mustn’t touch that – it’s hot!
• Question: Must + subject + base verb?
  Example: Must we wear uniforms?

🧠 Summary Chart

📌 Notes

• All three modals are followed by the base form of the verb (without "to").
• Modal verbs do not take "s" for third person singular.
• Modals don’t use “do/does/did” for questions and negatives.