Should you want to recreate the green wildfire from Game of Thrones, you’ll have to consult the works of one Mr. R.R. Martin.
But if you just want to make some good old fashioned rain fire, all you’ll need is this: 2Fe+3O2= 2Fe2O3.
The guys start off by touching a 9-volt battery to the steel wool to send a current through it. Once the thin steel wire heats up to about 700 degrees and begins interacting with the oxygen in the air, iron oxide is created, which in turns leads to a fiery reaction that sends flaming chunks of steel wool tumbling through the air in a waterfall of picturesque sparks.
And there you have it. Fire rain:
Before trying this at home, two words of advice: fire extinguisher.