"Heavy Metal" is the 23rd episode of the second season of Superman: The Animated Series, and the 36th of the overall series. It depicts the debut of the character Steel. After the failure of his previous battle suit, John Henry Irons has decided to work on a new suit, safer than the last one. This suit is soon put to the test when Metallo returns and nearly kills Superman. Now Irons has to don his suit to try and defeat the evil cyborg.
John Henry Irons carefully removes a steel helmet from a furnace and cools it in a bucket of water. He then adds the helmet to a full suit of powered armor. His niece Natasha inquires if he's ready to use the suit to be a hero but he claims that he still needs to do more testing. A news report comes on and tells about the appearance of a super strong villain that has been robbing various banks in the area and this thief supposedly has ties to Intergang.
Elsewhere, a bank is being robbed by three masked men. One of them displays incredible strength by tearing the safe open with his bare hands. An alarm is sounded and the police come to foil the robbery. However, the strong member of the gang manages to make short work of the police.
Back near his lab, Irons tests an arm-mounted laser and sees that it works. The chase goes past him and he decides to intervene. He blasts out a tire on the thieves' truck and manages to deflect their bullets with his armored armband. However, a flaw in the armor causes the laser to break. While Irons tries to fix it, the thieves find him and prepare to shoot him. Fortunately, Superman shows up and saves Irons. Another thief shows up and feigns surrender. However, when Superman tries to apprehend him, the thief punches him. The thief then removes his mask revealing that he's Metallo.
Superman starts fighting Metallo using various weapons that allow him to keep his distance. For a time this seems to work, but Metallo shows off a new feature: the ability to fire beams of Kryptonite radiation. With this new ability, Metallo manages to capture Superman and begins to bombard him with radiation. Irons tries to stop him but is unsuccessful. Fortunately, Natasha rams into Metallo with the van hurling him away. Irons grabs Superman and the group drives off. Unfortunately, Metallo manages to capture a police car and gives chase.
After some stunt driving, the group manages to escape and get to Irons' lab. Irons carries Superman out of the van causing a stir in the neighborhood but they still manage to get into the lab. In the lab, Irons puts Superman under a light generator to feed him yellow sunlight.
Metallo shows up in the neighborhood and demands that the people tell him where Superman is. When no one speaks up, Metallo and his men start causing random destruction. The people manage to hold out for a time but are eventually forced to talk. Fortunately, before Metallo can get to Superman, Irons comes out in full armor and introduces himself as "Steel". Metallo's men attack Steel but he easily manages to defeat them. He then fights Metallo, who is a lot harder than his men and the fight eventually brings him into Irons' lab.
They continue, but Metallo proves to be more than a match for the new super hero. He manages to trap Steel and grab hold of his hammer. He nearly hits Steel with his own hammer but Superman intervenes. The victory is short-lived however, Metallo resumes blasting Superman with his Kryptonite and this times it seems like he'll finish his enemy off. Before Metallo can finish the job, Steel hurls his hammer directly into his chest, destroying the Kryptonite rock. Superman recovers and thanks Steel for his help.
- Irons and Superman both refer to their last conversation in "Prototype", which introduced the precursor to Irons's battlesuit. Natasha also refers to Irons quitting his job with LexCorp in that episode.
- Bibbo Bibbowski mentions (and takes some credit for) the time Superman fought Titano in "Monkey Fun".
- Metallo states that he was rescued from Raknaveek by Intergang after Superman left him there, buried under solidified lava without his Kryptonite battery, in "Action Figures".
Home video releases
- Superman: The Animated Series, Volume Two (DVD)
- Superman: The Complete Animated Series (DVD)
- Best of Warner Bros. 25 Cartoon Collection: DC Comics (DVD)
- When John Irons is testing out his wrist-mounted laser gun, he blows up a few objects, causing an explosion that features reused footage from a scene of "My Girl", in which Mr. Eelan blows up a vat of hot lead from its support.
- In "Action Figures", Metallo had lost all of his artificial flesh. Intergang seems to have replaced it, but it is unknown why they only replaced part of it, essentially reproducing the look Metallo had in "The Way of All Flesh".
- The mouth plate on Steel's helmet can move even though it was a single solid piece at the start of the episode.
- As Natasha turns up the volume during the news report, Superman's left shoulder can be seen, despite the fact that Clark Kent is watching the same report at the Daily Planet.
- Though this version of Steel is based off the character in the comics, his origin is different. In the comics, Doctor Irons hadn't built his suit until the Death of Superman. Another difference of this version of Steel is that he doesn't wear the cape and shield of Superman.
- The 5 on Irons' shirt is a reference to Superman's S shield.
- Although Natasha becomes another incarnation of Steel in the comics, she never does in the cartoons.
- Spunky Spencer from the Batman: The Animated Series episode "Baby-Doll" can be seen in the crowd when Irons' car stops and when Metallo lies defeated.
- Bruce Timm considers this to be the one of the worst episodes of the DC Animated Universe. 
|Tim Daly||Superman/Clark Kent|
|Michael Dorn||Steel/John Henry Irons|
|Lauren Tom||Angela Chen|
|Michael Donovan||News Anchor|
|Marc Drotman||Bank Manager|
|Vernee Watson-Johnson||Female Neighbor|
Natasha: You're gonna be home on time for dinner tonight?
Reporter: Daily Planet Media news reporter Angela Chen has just located a witness to today's multi-million dollar diamond district robbery. We go to her now live; Angela?
John Irons: That's taking out the trash, Superman.
Metallo: Remember how you left me, Superman? Buried in rock. I couldn't move! I couldn't see! I couldn't hear! But I could think! And all I thought about was how I was going to make you pay! Goodbye, hero.
Metallo: You ought to be paying attention my friend! The tabloids will be all over you! You're about to become famous. The man who watched Superman die!
Metallo: Somebody speak up! Or I'll tear this neighborhood apart! Brick by brick.
Metallo: Now, where is Superman?!
Metallo: Well, what have we here?
Metallo: Sorry, Steel. I've still got some business in the hood.
Natasha: Come on, Superman! This ain't no tanning salon!
Natasha: He's got Superman. He's gonna kill 'em!
Superman: Well, Steel, you're gonna be getting this a lot, so you might as well hear it from me first.