Unit 2: Modal Verbs
Learning Objectives
- Identify the four main functions of modal verbs in English
- Distinguish between possibility, ability, obligation, and permission
- Use the tool to see how modals change a sentence across past, present, and future
What Are Modal Verbs?
Modal verbs are a special group of auxiliary verbs that express attitude towards an action rather than describing the action itself. They do not change form (no -s, -ed, or -ing) and are always followed by a bare infinitive.
The core English modals are:
can • could • may • might • shall • should • will • would • must
Each modal can express more than one meaning depending on context. In this unit we focus on four key functions: possibility, ability, obligation, and permission.
The Four Functions
Expand each function to see which modals are used and when.
Modals: can, could, may, might
| Time | Example |
|---|---|
| Past | She could have missed the bus. |
| Present | It may rain later. |
| Future | We might visit Tokyo next year. |
Modals: can, could, be able to
| Time | Example |
|---|---|
| Past | He could swim when he was five. |
| Present | She can speak three languages. |
| Future | They will be able to join us next week. |
Modals: must, should, shall, have to
| Time | Example |
|---|---|
| Past | You should have called first. |
| Present | Students must submit their work by Friday. |
| Future | Everyone will have to register in advance. |
Modals: can, could, may, might
| Time | Example |
|---|---|
| Past | Students might use dictionaries in old exams. |
| Present | You may leave early today. |
| Future | Members may bring one guest next term. |
Tool: Modal Verb Transformer
Enter a simple sentence, then click a modal function to see the sentence rewritten in the past, present, and future using the appropriate modal verb.
Try: "She sings beautifully." or "He reads quickly."
Check Your Understanding
Which modal verb expresses present ABILITY?
'You must submit the report by Friday.' This sentence expresses…
Which sentence asks for permission most politely?
Watch
Video coming soon
Review
| Function | Common modals |
|---|---|
| Possibility | might, may, could, can |
| Ability | can (present), could (past), will be able to (future) |
| Obligation | must, should, shall, will have to |
| Permission | may (formal), can (informal), could (polite) |
The tool simplifies modal usage into past, present, and future to make the patterns visible. In real English, the relationship between modals and time is more nuanced — for example, could can express past ability, present possibility, or polite requests depending on context.
Proceed to Unit 3: Participle Clauses when ready.