Ray Bradbury's novel Fahrenheit 451 is a dystopian novel which delineates the dangers of a society mired in conspicuous and mindless materialism; a society degraded by its distaste of intellectual stimulation and independent thought is a society that is closed and sterile. People in Fahrenheit 451 are told that books are the enemy; they are fed mindless entertainment everyday. They are taught to fear the "offensive" things that books might possibly teach them. Montag, the main character who is a fireman, lives with his wife, Mildred, who is oblivious to his dissatisfaction with their lives. He tries to read to her from books he hides in their house, but she is not interested. Instead, she turns him in and their house is slated to be burned.
Although he is shocked and angry that Mildred turns him in, his sense of outrage is soon supplanted by his desire to burn everything that reminds him of his senseless existence. He aims the flamethrower at their twin beds, reminders of his cold, loveless marriage. He sees the beds light up "with more heat and passion... than he would have supposed them to contain." If he is supposed to burn up his own house, he would derive a grim pleasure from erasing all traces of a sham existence. After all, he decides that there is no longer any reason to even have the house: Mildred, "who had gone and quite forgotten him already" would probably be more interested in listening to her Seashell radio than remembering the bonds of loyalty or the promises of any marriage vows made between them.
The fire is cathartic; he feels he is getting rid of both the problem and the solution. He vents his pent-up frustrations, grief and anger as he burns up the "great idiot monsters," the parlor wall-sized television screens "with their white thoughts and their snowy dreams," the monsters that claimed more of his wife's attention than he ever did.
If there was no solution, well then, now there was no problem either. Fire was best for everything!
So, the fire is both an act of catharsis as well as an act of rebellion. He wants a better existence than what the government has decided for him.
Hope this helps. Thanks for the question!