So far you know three modal verbs: können, müssen and wollen:

The modal verb können expresses an ability or possibility:
Nico kann studieren. (He has the mental ability and the financial means to study.)
In the singular, the vowel ö changes to a.

The modal verb müssen expresses a necessity or compulsion:
Nico muss studieren. (His parents are putting pressure on him. If he does not study this will have negative consequences for him.)
In the singular the vowel ü changes to u.

The modal verb wollen expresses a desire or intention:
Nico will studieren. (He wishes or plans to study.)
In the singular the vowel o changes to i.

There is one more modal verb that is used to express wishes, möchten (mögen): 
Nico möchte studieren.

The modal verbs wollen and möchten are similar in meaning. Both describe something that one would like to have or do, but with a different emphasis.

• Ich möchte … describes a wish and sounds more polite.
• Ich will … is stronger and more definite.

The verb möchten is conjugated differently from the other modal verbs. This is because möchten is a special form of the verb mögen. But here too, the first- and third-person singular are identical.