The Iron Giant

In 1957, during the Cold War, a gigantic extraterrestrial robot crash-lands off the coast of Rockwell, Maine. The following night, nine-year-old Hogarth Hughes investigates reports of power outages and discovers the Giant feeding on electrical lines at a substation. Though initially frightened, Hogarth later returns to save the Giant from electrocution.
Hogarth befriends the Giant, discovering him to be gentle, curious and childlike. The Giant eats railroad tracks, oblivious to an oncoming train which collides with and damages him. The Giant's scattered pieces automatically return to him, allowing him to self-repair. Hogarth shelters the Giant at his home and shows him his comic books, explaining the difference between heroes and weapons and comparing him to Superman.
Incidents related to the Giant attract the attention of the paranoid federal agent Kent Mansley, who arrives in Rockwell to investigate. While initially skeptical, Mansley eventually believes in the Giant's existence and views him as a national threat. Suspecting Hogarth knows more than he admits, Mansley rents a room in the home of Hogarth and his widowed mother Annie to watch him. To keep the Giant safe and well-fed, Hogarth brings him to a wrecking yard owned by beatnik artist Dean McCoppin, who reluctantly agrees to hide him. When Hogarth and the Giant witness hunters killing a deer, Hogarth explains death to the Giant, which unsettles him.
After discovering a photograph proving Hogarth's connection to the Giant, Mansley interrogates him, then summons U.S. Army General Shannon Rogard and soldiers to the scrapyard. Forewarned, Dean disguises the Giant as a sculpture to deceive the soldiers into leaving. Later, when Hogarth playfully points a water gun at the Giant, he instinctively activates one of his defensive systems. Horrified that he could be lethal, the Giant flees toward the town in shame. Dean realizes the Giant can only attack in self-defense, and he and Hogarth pursue him.
In Rockwell, the Giant rescues a pair of boys falling from a building, briefly winning the support of the townspeople as he reunites with Hogarth. Mansley spots him and urges Rogard to attack. In the ensuing confrontation, Hogarth is rendered unconscious and the Giant, believing Hogarth has died, enters a heavily-armed battle mode and retaliates against the soldiers. When conventional weapons fail, Mansley persuades Rogard to launch a nuclear missile from the USS Nautilus.
Hogarth regains consciousness and subdues the Giant by reminding him that he can choose who he wants to be. Dean convinces Rogard to stand down, but an enraged Mansley impulsively orders the missile launch before realizing the missile is targeted towards Rockwell, and will destroy the town and its inhabitants. Mansley attempts to flee, but is stopped by the Giant and promptly secured. Determined to save the town, the Giant bids farewell to Hogarth and flies upward to intercept the missile. The Giant collides with it high above Earth and harmlessly detonates it in the exosphere, apparently sacrificing himself.
Months later, Annie and Dean admire Dean's memorial statue of the Giant in the town park. Hogarth receives a package from Rogard containing a single screw recovered from the Giant, the sole remnant found following the Giant's sacrifice. That night, the screw starts moving; Hogarth remembers the Giant's ability to reassemble himself and happily allows it to roll out of his bedroom window. Far away on the Langjökull glacier in Iceland, the Giant's head smiles as his scattered parts converge for his reassembly.