Many of the scary things our speaker faces on this crazy night have to do with the natural world. He imagines hostile natural forces all around him, surrounding his peaceful, civilized room, just waiting to break in. The dark night, the sound of the wind…they are all threatening and unfathomable. Then nature does break in, in the form of that arrogant, talkative bird. This is the big central confrontation of the poem, and it brings the idea of a conflict between man and nature right to the front.
The raven and the rest of the natural world don't want to hurt or destroy the narrator at all. In fact, it is only his growing madness that makes the raven appear evil.