The staple of Godzilla, his atomic breath could easily compared to a flamethrower. His spines light up as he gathers up energy from his body and unleashes it upon his foes. It’s unknown as to what lights up his fuel source or what his fuel source is even. The Heisei Series establishes his body as running on what is akin to a nuclear reactor so the only explanation I could formulate is that Godzilla can somehow use a process of Nuclear Fission to power up his breath.
Other iterations of Godzilla (such as his appearance in GMK:Giant Monsters All Out Attack), his atomic breath has the destructive force of a miniature atomic bomb. Due to Newton’s Third Law, which states that for every force there must be an equal and opposite reaction force, Godzilla’s head should theoretically be blasted off his shoulders from the mere force it would take to create a nuclear explosion like that.
