We use Modal verbs to express: Abilities, Requests, Advice, Offers, Deductions, Commands, and Probabilities. The same modal verb can have different meanings: i.e. 
Can I borrow your CD?            Request         
I can speak German well!       Ability
These verbs are often called  modal auxiliary verbs, because they don’t need an auxiliary to form a negative or interrogative phrase.
ex: I Can’t speak Spanish well. not  I do not can speak Spanish well.
Modal verbs can be can be formed in the past, present or future: the forms may change accordingly:
This modal verb is usually used in the present form. However to be noted that when making requestscould/mayis a more polite form to use, whilstwouldeven if not commonly used these days is more of an order/request.
ex. Would you open the window please?
      May I have a glass of water please? (polite form)

Note Important! Modal verbs never go with to and no  s  in the third person.
In this section we are going to look at the modal verbs that are used to give advice: