Montag is a prime example of character development. When we first meet him, he is a devotee of the firemen. He loves his job and never questions society at all. Once he meets Clarisse, we see a new side of him brought to light. She encourages him to question why things are the way they are. Once his wife attemtps suicide, Montag really begins questioning the monotony and drabness which his society is enveloped by. Why isn't anyone questioning the war that's about to explore, or even thinking about it? Why aren't books allowed? He betrays himself by asking these questions to Beatty and then his development is complete, as he becomes a rebel and a fugitive and finally, at the novel's resolution, decides to rebuild society.
There are definitely contrasts between Guy and Beatty. Beatty stands firm in his defense of society's decisions regarding the banning of books and the "equalizing" of people. Yet they may not be so different after all. Beatty does seem to allow Guy to kill him, which Guy later interprets as Beatty's wish for death. Guy eventually realizes that Beatty was not happy, either.