Modal verbs.
I've started learning modal verbs and I met a problem. There are a lot of verbs and some of their I bad understood. What modal verbs do you often use? What verbs I must to know?
P.S. Did I right use a present perfect in the first sentence?
Ty

Question

Modal verbs.
I've started learning modal verbs and I met a problem. There are a lot of verbs and some of their I bad understood. What modal verbs do you often use? What verbs I must to know? 
P.S. Did I right use a present perfect in the first sentence? 
Ty

Answer

modal verbs can change the meaning of a sentence; so I think you should be aware of all...some of them are interchangeables, but there are times in which they can change the whole meaning.