Here you are a page with a good explanation of the difference between the most common modals: CAN - COULD - MAY - MIGHT. It's in Spanish and it's also quite clear, with a few examples, so you can have a look to check your knowledge of English modals. There is a list of idioms or common expressions which are quite interesting as well. To go to the link, click HERE. Once you've read this, try to do some exercises like the ones you can find here:
- exercise 1 : quite easy but it's some practice
- exercise 2 : some more exercises
- exercise 3 : this page is to go further in your practice and more modals are included. There is a tutorial and exercises. It's quite useful.
As you can see the level is not so high but it's worth revising simple things from time to time to check you still do them properly.
See you in short time!
PD: this post is also available on the other blog I have for intermediate students: