Fyrus
Fyrus is the boss of the Goron Mines.
As with most bosses in the Zelda series, you must first make Fyrus vulnerable and then attack his weak point repeatedly to defeat him. To do this, you will need your Hero's Bow and the Iron Boots. First, attack the glowing jewel on his head with an arrow. This will temporarily distract him and give you the time you need to knock him over. Equip the Iron Boots and grab the end of one of the chains attached to his arms and pull. This will cause Fyrus to fall over. Quickly run to the front of the large creature and repeatedly attack the jewel on his forehead with your sword. Repeat the process until he is defeated.