This article is additional to the main page dedicated to Modal Verbs.
When we want to make a request we use modal verbs 'can', 'could' and 'would'. They all can be used interchangeably, but you need to remember that they have a different level of politeness.
Would
The most polite way to make a request is to use the modal 'would'. But be careful - this modal has a special grammatical way of usage.
We take a phrase 'would you mind' than place a main verb with -ing ending after it.
Would you mind opening the window?
Would you mind turning on the light?
Could
Using the modal 'could' is also a rather polite way to make a request.
Could you give me a piece of advice, please?
Could you take my bag, please? It's very heavy.
Can
The modal verb 'can' is the most common way to make a request but less polite than 'could' and 'would'.
Can you take my bag?
Can you help me with this programme?