a. Dare is used as a transitive verb.
As a transitive verb-- dare means to challenge.
b. It is used as an intransitive verb of incomplete prediction.
As a intransitive verb-- dare means 'to venture', to have courage.
Note: Sometimes durst is used and sometimes dared in the past tense, provided it is followed by a negative.
Note: The idiom "I dare say" conveys the meaning of perhaps.
a. He dare not leave the room.
b. He dares me to fight.
c. He durst not leave the room.
d. I dare say, he is a bad man.