Iron Man,

a giant "metal man" of unknown origin who rains destruction on the countryside by eating industrial farm equipment, before befriending a small boy and defending the world from a dragon from outer space. Expanding the narrative beyond a criticism of warfare and inter-human conflict, Hughes later wrote a sequel, The Iron Woman (1993), describing retribution based on environmental themes related to pollution.

Not to mention all these movies and books about androids and how to define "human" and "soul." I need to read the Ted Hughes novel! It sounds like the source of Iron Giant. Then again, Neil Gaiman had a book with a boy wizard and his owl that J.K. Rowling insists she never saw. I've had story ideas I failed to write or publish and later someone else had the same thing. The radio was invented by at least three men unbeknownst to each other, but only one of them is now known as the father of radio.
I'll bet you've read The Selfish Giant by Oscar Wilde (1888). Hey, Iron Giant, similar theme...

A giant, who finds children from the village playing in his beautiful garden, chases them away and builds a high wall around his estate. Then Spring leaves the garden and Winter returns and remains there permanently until the children manage to slip through a hole in the wall. Spring then returns. The giant mellows and allows the children to play in his garden whenever they want.