Despite his insatiable hunger for metal, the Iron Giant is quite gentle and good-natured, though the townspeople are too frightened of him to realize it. So they capture him and put him in a scrapyard, where he happily stuffs himself with stoves and bicycles.

The people forget about the Iron Giant until a big shadow blocks out the sun. A giant space-bat the size of Australia is hovering over the earth, ready to destroy it. The earth needs a hero. But who -- or what -- is big enough and do battle with the hideous creature from outer space?