Indra is the king of the Gods and in the same tier as Agni. I look at it as Brahma, Vishnu, and Shiva are tier one, then there is a tier of Gods below them that are the ancient Vedic Gods like Agni and Indra. I’m not sure where Ganesha falls in, though, since he is probably the most worshiped of any God, yet is not part of the trinity! Maybe he is tier 1.5.
Indra was very important in ancient times as a war God and also as a God of weather. He controls thunder and lightning, and bears some resemblance to Zeus.
These days he is most often referenced for being the father of Arjuna, the great archer whose conversation with Krishna is the Hindu holy book The Bhagavad Gita.
In the Rig Veda, Indra is the king of the gods and ruler of the heavens. Indra is the god of thunder and rain and a great warrior, a symbol of courage and strength. He leads the Deva (the gods who form and maintain Heaven) and the elements, such as Agni (Fire), Varuna (Water) and Surya (Sun), and constantly wages war against the opponents of the gods, the demon-like Asuras. –Wikipedia
There are lots of stories of the exploits and battles of Indra!
I think in the current age we have less need for Him, since our societies are no longer based on war and conquest.