He led a band of monkeys, or ape-like creatures, who gave very important support to Rāma inside the rescue of Sītā from Rāvaṇa's kingdom of Laṅkā. He's a symbol of strength and loyalty, and is patron of wrestlers. The Panchamukhi Hanuman Kavach is also commonly heard and meditated on. https://www.youtube.com/watch?v=ufkmD95y7fE