Pyromane is the French word for "pyromaniac", a person obsessed with setting fires. It's a very dramatic and unusual word to find in a love song, making it instantly memorable.
In "Tout Donner", Gims uses it metaphorically. After singing "J'pourrais tout flamber pour toi" (I could set everything ablaze for you), he clarifies "Pourtant je n'suis pas pyromane" (And yet I'm not a pyromaniac). He uses the imagery of fire not for destruction, but to express the all-consuming intensity of his love.
Gims isn't messing around in this song. He lays all his cards on the table in a huge, dramatic declaration of love. He tells his partner, "Ne me demande pas la Lune / J'ai beaucoup mieux pour toi" (Don't ask me for the moon / I have much better for you), promising something more real than clichés. This isn't a light-hearted crush; he says his steps are heavy because he's carried a lot of burdens, and now she is everything to him. The chorus is a powerful, repeated promise: "Allez je t'ai tout donné / Tu es tout ce que j'ai" (Come on, I gave you everything / You are all I have).
He mixes intense devotion with a bit of swagger. He claims her heart completely with the line "Ce que t'as dans la poitrine, c'est à moi" (What you have in your chest is mine). He even suggests a wild, ride-or-die partnership where "tous les deux on foncera dans l'mur" (together we'll crash into the wall). He sees their love as a powerful force, wanting to be her "allié" (ally) and an "alien" to their enemies. It's a song about giving absolutely everything to one person, the one who is both his sickness and his cure.