Then he'll be stunned like a regular one and you can use the Light Arrow and sword on him.  Eventually you'll defeat him.  I'm not going to give away the rest of the game after this, but if you get stuck, here are some hints:  1) Take off those Hover Boots! 2) Follow instructions, and be quick about it 3) If you're looking for a weak spot, try the tail 3) What Light Arrows can't kill, they can stun 4) If you didn't get the Big Goron's sword, you may need the Megaton Hammer.   Enjoy the ending of this awesome game!