Guy Montag—simply referred to as "Montag" throughout the bulk of the narrative—is the protagonist of Fahrenheit 451. The events of the novel are told from his perspective, and the plot is primarily driven by the evolution of his personal choices as he navigates the rigid, dystopian world around him.

At the beginning of the story, Montag is a third-generation fireman. He spends his workday burning books—all of which are illegal contraband—for the fire department. He is obedient to the fire captain and content in his work, and he never stops to wonder why things are the way they are. When he meets a new neighbor, seventeen-year-old Clarisse McLellan, on his way home from the fire station one night, she challenges his traditional thinking, and Montag's view of the world begins to shift. Clarisse is different than anybody he's met before—she is thoughtful and inquisitive, and she encourages Montag to ask questions about the world around him. Her perspective leaves an impression on him, and he slowly begins to question the established rules of society in ways he never has before.

As their friendship develops, Montag's sense of the world around him changes. The system that used to seem efficient and tidy begins, instead, to feel authoritarian and oppressive. As he becomes more and more disillusioned with the social order of his environment, his outward behavior begins to change, too: he begins hoarding books in secret, acting strangely around others, and actively seeking out the friendship and guidance of those who live in contravention to established norms. These choices ultimately upturn life as he knows it. By the book's close, Montag's perspective on life has shifted dramatically, and he is living outside of society entirely.