When are modal verbs used? What special conditions do modal verbs show? Here’s a list of when to use modal verbs, along with examples:
Likelihood Some things seem likely, but we don’t know for sure. In these cases, you can use the modal verbs should and must to show probability without certainty.
Her parents must be so proud. My baby brother should be asleep by now. Possibility In situations when something is possible but not certain, use the modal verbs could, may, or might.
Judging by the clouds, it might rain today. She may become the youngest pro soccer player ever. Ability The modal verb can shows whether or not the subject is able to do something, such as perform an action or demonstrate an ability. Likewise, the negative form, cannot or can’t, shows that the subject is unable to do something.
She can speak three languages, but none of them well. You can lead a horse to water, but you can’t make it drink. Asking permission If you want to ask permission to do something, start your question with can, may, or could. Traditionally, in more formal and polite usage, may is better for permission; if you ask “can I go to the bathroom?” it could be misinterpreted as, “do I have the ability to go to the bathroom?” (However, in modern usage may and can are both perfectly acceptable options when describing possibility or permission.)
May I leave early today? Could I play too? Request Similarly, if you want to ask someone else to do something, start your question with will, would, can, or could.
Would you get that box off the top shelf? Will you turn that music down?