In speaking and writing, helping verbs may act as modals. Modals are used to express permission, possibility, necessity, or intentions of speakers and writers. Sometimes, modals are used to indicate the opinion of the speaker about an event.
| Modals and examples | How they are used |
|---|---|
| According to the news, it may rain tonight. You may now go to the office. |
Use the modal may to indicate:
|
| Camels can go great distances without water. | Use can to denote the ability to do something. |
| They must be in school by now. She must have done well on the test. |
Use must plus the verb when you are 100% (or almost 100%) sure that something is the case. |
| She might come this evening. Jack might have gone to France. |
Use might to express an opinion that you think has a good possibility of being true. |
| Jane could be at work. Peter could have arrived late. |
Use could to express a possibility which is one of many. |
| You can’t be serious! | Use can’t to express an opinion that you are completely sure is not true. |
