In the 1950s town of Rockwell, Maine, a young boy named Hogarth Hughes discovers a giant metal robot that has fallen from space. Initially startled, Hogarth soon realizes that the Iron Giant is harmless and even friendly. Despite their immediate bond, Hogarth decides to keep the giant a secret to protect him from potential threats. With the help of local beatnik artist Dean McCoppin, Hogarth hides the Iron Giant in Dean's scrap yard, allowing them to form a close friendship. They teach the giant about humanity while also attempting to keep him out of sight.

As the U.S. government becomes aware of strange happenings in Rockwell, Agent Kent Mansley arrives to investigate. Suspicious and driven by Cold War paranoia, Mansley will stop at nothing to find the rumored giant. He closely monitors Hogarth, causing the situation to escalate. The bond between Hogarth and the Iron Giant is put to the test as they navigate growing dangers and misunderstandings. As tensions rise, the true nature of the Iron Giant and his purpose on Earth begin to unravel, culminating in a situation that challenges the very essence of heroism and friendship.