Montag's belief in his work, his understanding of the power of his position as a fireman, and the knowledge that he was providing a service to the community are all depicted in this quote.
"It was a pleasure to burn. It was a special pleasure to see things eaten, to see things blackened and changed. With the brass nozzle in his fists, with this great python spitting its venomous kerosene upon the world, the blood pounded in his head, and his hands were the hands of some amazing conductor playing all the symphonies of blazing and burning to bring down the tatters and charcoal ruins of history." (Bradbury)
Montag's joy and pleasure in watching the process unfold, the unleashing of the great flame, the power it possess to crush and destroy to eliminate, wipe away, reduce to ashes and dust that which stood before it, was intoxicating to Montag and it gave him a sense of great power.
Montag enjoys his power, which really is based on his obedience to the state, as long as his base of knowledge remains committed to the state, he will remain powerful. Once he decides that knowledge is a tool that provides opportunities for free thought, he is in trouble.
In Fahrenheit 451, the power base is conformity, in one's sameness there is power as Montag's fireman experiences. Once he decides to transform into an individual capable of free thoughts outside the state's belief system and rules, he becomes a rogue, a wanted man, an outlaw, his power is reduced but his knowledge is increased. Knowledge in this book is really dangerous.