ESL Grammar: Verbs Tenses - Modal Verbs, Can, Could, May, Might, Must, Should

What It Is

Modal verbs are special verbs that express possibility, ability, permission, obligation, and advice. They are used to talk about things that are not certain or absolute. For example, "I can speak English" is different from "I speak English," because "can" shows that speaking English is possible for me. ESL learners often struggle with modal verbs because they have many different forms and uses.

Key Rules

• Can is used for ability and permission: "I can speak English" (ability), "You can go to the party" (permission).
• Could is used for past ability and past permission: "I could speak English when I was a child" (past ability), "You could go to the party last night" (past permission).
• May is used for permission and possibility: "You may go to the party" (permission), "It may rain tomorrow" (possibility).
• Might is used for possibility and uncertainty: "It might rain tomorrow" (possibility), "I might be late" (uncertainty).
• Must is used for obligation and necessity: "You must be here at 5 o'clock" (obligation), "This cake must be eaten today" (necessity).
• Should is used for advice and recommendation: "You should eat more fruits" (advice), "This book should be read by everyone" (recommendation).
• Can and could are often confused with can meaning "to be able to": "I can run fast" (ability), "I can speak English" (ability).
• May and might are often confused with each other: "It may rain tomorrow" (possibility), "It might rain tomorrow" (possibility).
• Must is often confused with have to: "You must be here at 5 o'clock" (obligation), "I have to go to the store" (obligation).
• Should is often confused with ought to: "You should eat more fruits" (advice), "You ought to eat more fruits" (advice).
• Can, could, may, might, must, and should are all irregular verbs and have different forms in the past tense and past participle.
• Can and could are pronounced the same way: /kæn/ (KAN).
• May and might are pronounced the same way: /me?/ (MAY).
• Must is pronounced /m?st/ (MUST).
• Should is pronounced /d/ (SHOULD).

Common ESL Errors

• Error: "I can go to the party." Why it happens: Interference from L1, overgeneralization. Correction: "You may go to the party" (permission).
• Error: "I could speak English when I was a child." Why it happens: Overgeneralization. Correction: "I could speak English when I was a child" (correct, but note that this sentence is not common).
• Error: "You must go to the party." Why it happens: Interference from L1, overgeneralization. Correction: "You should go to the party" (advice).

Practice Exercises

1. Fill in the blank: "I can speak English, but I'm not a native speaker." Correct answer: "I can speak English, but I'm not a native speaker." Reason: This sentence uses can to show ability.
2. Fill in the blank: "You may go to the party if you want to." Correct answer: "You may go to the party if you want to." Reason: This sentence uses may to show permission.
3. Fill in the blank: "It might rain tomorrow, so bring an umbrella." Correct answer: "It might rain tomorrow, so bring an umbrella." Reason: This sentence uses might to show possibility.

Last-Minute Revision

Can and could are often confused with each other.
May and might are often confused with each other.
Must is often confused with have to.
Should is often confused with ought to.
Can, could, may, might, must, and should are all irregular verbs and have different forms in the past tense and past participle.
Can and could are pronounced the same way: /kæn/ (KAN).
May and might are pronounced the same way: /me?/ (MAY).
Must is pronounced /m?st/ (MUST).
Should is pronounced /d/ (SHOULD).
Can is used for ability and permission, but not for obligation or necessity.
Could is used for past ability and past permission, but not for past obligation or past necessity.
May is used for permission and possibility, but not for obligation or necessity.
Might is used for possibility and uncertainty, but not for obligation or necessity.
Must is used for obligation and necessity, but not for permission or possibility.
Should is used for advice and recommendation, but not for permission or possibility.