The God of Fire, Agni, and the God of Rain, Varuna, were arguing about who was greater.
"Fire is greater than water!" said Agni.
"No!" said Varuna. "Water is greater than fire!"
They decided to have a contest to see who was right.
The God of Fire burned trees, crops and villages, but Varuna poured down rain and put out the fire. The God of Fire then fled into the mountain rocks, while rain kept pouring down.
Even now, Agni is hiding in the rocks; that's why when you strike rock with steel, sparks fly and you can make fire.
Inspired by: Heeramma and Venkataswami, or Folktales From India by M. N. Venkataswami
Notes: You can read more about the gods Agni and about Varuna at Wikipedia.