Didn't have time to post an elaborate explanation for my guess, so I'll do it now.
You've seen my kind before And now you've come to find me But as you will soon learn I'm as different as can be // It's not the first "giant head +hands" kinda boss in the Zelda series, and for a change, it is not an enemy and it doesn't wanna kill you. It's some sort of robotic device made by the Gods to challenge people to see if they're worthy of visiting frozen-in-time Hyrule Castle + getting the Master Sword.
You say you can't move on? Well isn't that just grand. Treat me to a delight, And I can lend a hand. He blocks the way to Hyrule Castle. Win the challenge, and he lets you through. Also, he has massive hands, but I don't know if that was intentional :p