Modal verbs, which express a likelihood, ability, permission, request, order etc., usually help main verbs to state the future. It is the reason they are categorised as auxiliary verbs in the context.

The present tense describes what's happening now. Depuis is used with the present tense to say how long something has been happening. Learn how to form sentences using the present tense. Key verbs - ...

Making polite requests are a part of daily life in a range of situations – we might be in a formal setting like an office, at a work party or we might be making a request because we need something.

We can also use might, may and could for talking about what we think was possible in the past. NASA says it may/might/could have been suitable for life in the past. We use the modal verbs must and can ...