Hit B to swing the fire sword. If you tap Up on the +Control Pad while wielding the blade and then hit B, you'll throw it.”
— Description • Nintendo Power (Volume #134)
Sword of Fire is a combination ability used in Kirby 64: The Crystal Shards made by mixing the Burning and Cutter abilities. With it, Kirby uses a flaming sword to attack enemies. Kirby can also throw the sword at enemies. The one catch is that when he is holding the fire sword, he can't fly. The sword can be used underwater.
Kirby takes a sword of flame out of his mouth and swings it.
Kirby raises his sword up, which can destroy most aerial enemies.
↑ + B
Kirby throws his sword straight forward and off the screen, flying through any enemies in its path, but colliding with walls.
Kirby uses a flaming sword that can be thrown by pressing Up and then either Left or Right on the + Control Pad[sic].”
— Description • Official Strategy guide
Kirby spits out a flaming sword that he can use against enemies and obstacles. To put the sword away, press ↑ then B.”