Definition:
The phrase "on fire" means something is literally burning with flames, like a house or a forest. However, it can also be used in a figurative way to describe something that is very exciting, successful, or energetic.
Literal Use:
"The house was on fire, and the firefighters arrived quickly to put it out."
Figurative Use:
"The basketball player was on fire last night, scoring 30 points in the game!"
"On fire" is a versatile phrase that can describe something that is literally burning or someone who is doing exceptionally well.