The Iron Giant is a huge humanoid behemoth, that is at least 50 feet tall. This advanced machine is capable of devouring metallic items and converting them into fuel. Its eyes are capable of shooting lasers. In addition it is capable of flight. It possesses another form that is armored and bristled with laser weapons, which possibly hints that it was originally a war mech of some kind. The machine has a strong amount of endurance as it was able to survive a nuclear missile at point range, with only its pieces scattered about the planet. The pieces are capable of reorganizing themselves and self-repair.
In the book of Ready Player One the Iron Giant made its appearance as a selectable reward for those who finished Black Tiger. However, no players acquired the mech and the robot was not seen during the Battle of Castle Anorak.
In the film, the Iron Giant appears in Aech's garage under construction but nearly complete, and is later activated as her avatar during the final battle for the OASIS. The giant is initially very effective during the battle, destroying many Sixers and IOI tanks with both its fists, feet, and laser weapons. When Mechagodzilla emerges onto the battlefield, the Giant immediately charges Mechagodzilla and blasts it with several bursts from its hand cannon. However, this has little effect, and it is quickly overpowered by the larger and more powerful Mechagodzilla, quickly being knocked down and then being heavily damaged by a burst of Mechagodzilla's atomic breath in the back. After Mechagodzilla is distracted by the arrival of Daito in a GUNDAM armor, the giant saves Parcival and Sho by leaping on the monster's back and pummeling its head, before revealing Art3mis in its hand, allowing her to get close to the enemy mecha's head to deliver the final blow and destroy it. Soon after, the giant sacrifices itself to serve as a bridge to allow the remaining members of the High 5 into the castle, sinking into the lava while giving a thumbs-up, a reference to Terminator 2: Judgement Day.
- The Iron Giant replaces Ultraman's role in the Ready Player One novel due to licensing issues, where he fights alongside the RX-78-2 Gundam against Mechagodzilla.
- When the Giant was first confirmed to be in the film, a controversy arose when many fans noted that the Giant was depicted in the promotional trailers as a weapon of war, which they claimed was a contradiction to the original 1999 film's Giant, who was a pacifist and despised violence. This version was likely modified for combat.
- Notably, the Giant does not take on the full-weapons form that he used in the original 1999 film against the Army during the OASIS battle. However, when the Giant attacks Mechagodzilla, its eyes turn red for a brief second as it activates its arm cannon. Thus, it is likely that Aech could have accessed the rest of the Giant's weapons and assume the weapons form, but had simply chosen not to.
- When the Giant is destroyed by being immersed in lava, he gives Parzival, Art3mis and Sho a thumbs up. This is similar to when the Terminator was destroyed in molten steel in Terminator 2: Judgment Day and gave John and Sarah Connor a thumbs up as he was destroyed.