The film stars the voices of Jennifer Aniston, Harry Connick Jr., Vin Diesel, James Gammon, Cloris Leachman, John Mahoney, Eli Marienthal, Christopher McDonald, and M. Emmet Walsh.

Set during the Cold War in 1957, the film centers on a young boy named Hogarth Hughes, who discovers and befriends a giant alien robot.

With the help of a beatnik artist named Dean McCoppin, Hogarth attempts to prevent the U.S. military and Kent Mansley, a paranoid federal agent, from finding and destroying the Giant.

The film's development began in 1994 as a musical with the involvement of the Who's Pete Townshend, though the project took root once Bird signed on as director and hired McCanlies to write the screenplay in 1996.

As he soars into the missile's path, the Giant remembers Hogarth's words, "You are who you choose to be," smiles contentedly, and declares himself "Superman" as he collides with the weapon.

The missile explodes in the atmosphere, saving Rockwell, its population, and the military forces nearby, while the Giant is presumably destroyed, leaving Hogarth, Dean, Annie, and Rogard devastated.

Johnston and Thomas, who were animators and members of Disney's Nine Old Men, were cited by Bird as inspirations for his career, which he honored by incorporating their voices, likenesses, and first names into the film.

[16] The origins of the film lie in the book The Iron Man (1968), by poet Ted Hughes, who wrote the novel for his children to comfort them in the wake of their mother Sylvia Plath's suicide.

[18] In 1991, Richard Bazley, who later became the film's lead animator, pitched a version of The Iron Man to Don Bluth while working at his studio in Ireland.

[18] After reading the original Iron Man book by Hughes, Bird was impressed with the mythology of the story and in addition, was given an unusual amount of creative control by Warner Bros.[18] This creative control involved introducing two new characters not present in the original book, Dean and Kent, setting the film in America, and discarding Townshend's musical ambitions (who did not care either way, reportedly remarking, "Well, whatever, I got paid").

[23] Bird considered the story difficult to develop due to its combination of unusual elements, such as "paranoid fifties sci-fi movies with the innocence of something like The Yearling".

[16] Nicknamed "The X-Factor" by story department head Jeffery Lynch, the producers gave him artistic freedom on various pieces of the film's script.

Although the production was watched closely, Bird commented "They did leave us alone if we kept it in control and showed them we were producing the film responsibly and getting it done on time and doing stuff that was good."

[14] Bird cited his favorite moment of the film's production as occurring in the editing room, when the crew gathered to test a sequence in which the Giant learns what a soul is.

He made sure to spread out the work on scenes between experienced and younger animators, noting, "You overburden your strongest people and underburden the others [if you let your top talent monopolize the best assignments].

Whiting strove for colors both evocative of the time period in which the film is set and also representative of its emotional tone; for example, Hogarth's room is designed to reflect his "youth and sense of wonder".

[35] Bird later recalled that he clashed with executives who wished to add characters, such as a sidekick dog, set the film in the present day, and include a soundtrack of hip hop.

Bird was against this for a multitude of reasons, mainly because he felt that the logo did not fit the tone of the movie, and eventually got confirmation that executives Bob Daley and Terry Semel agreed.

In researching its source material, he learned that Hughes wrote The Iron Man as a means of comforting his children after his wife, Sylvia Plath, died by suicide, specifically through the metaphor of the title character being able to re-assemble itself after being damaged.

The website's critics consensus reads, "The endearing Iron Giant tackles ambitious topics and complex human relationships with a steady hand and beautifully animated direction from Brad Bird.

[46] Kenneth Turan of the Los Angeles Times called it "straight-arrow and subversive, [and] made with simplicity as well as sophistication," writing, "it feels like a classic even though it's just out of the box.

"[62] The New Yorker reviewer Michael Sragow dubbed it a "modern fairy tale", writing, "The movie provides a master class in the use of scale and perspective—and in its power to open up a viewer's heart and mind.

"[63] Time's Richard Schickel deemed it "a smart live-and-let-live parable, full of glancing, acute observations on all kinds of big subjects—life, death, the military-industrial complex.

"[69] Peter Stack of the San Francisco Chronicle agreed that the storytelling was far superior to other animated films, and cited the characters as plausible and noted the richness of moral themes.

[70] Jeff Millar of the Houston Chronicle agreed with the basic techniques as well, and concluded the voice cast excelled with a great script by Tim McCanlies.

[71] The Washington Post's Stephen Hunter, while giving the film 4 out of 5 stars, opined, "The movie — as beautifully drawn, as sleek and engaging as it is — has the annoyance of incredible smugness.

"[72] The Iron Giant opened at Mann's Chinese Theater in Los Angeles on July 31, 1999, with a special ceremony preceding the screening in which a concrete slab bearing the title character's footprint was commemorated.

[84] In the Lego Movie spin-off series Unikitty!, the episode entitled "Kaiju Kitty" references the film's climatic moment of the Giant being blown up by the missile.

[88] A remastered and extended cut of the film, named the Signature Edition, was shown in one-off screenings across the United States and Canada on September 30, 2015, and October 4, 2015.

[89] The edition is approximately two minutes longer than the original cut, and features a brief scene with Annie and Dean in the cafe and the Giant's dream sequence.