Ray Bradbury uses the character Montag to convey several messages.
First, he conveys the message that rebirth is possible. Montag is certainly the character who most demonstrates this concept. Not only does he change throughout the course of the novel, but he is the character that readers follow. We learn his thoughts and hear all of his words. We see Montag's rebirth as he escapes the system and then begins life anew with purpose as he joins the group of transient men.
Second, he conveys again through Montag, that society as it is, is unacceptable. At the time of writing, Bradbury feared what our society would do with too much technology. This book seems to suggest that people might lose control of much needed relationships. It suggests that thought would become less necessary. The dystopian society that results is severely unattractive to the reader.