Metal Muncher

Well, that's one way to get more iron in your diet...

"Hey, big metal guy! I got food here for ya! Metal! Crunchy, delicious metal! Come and get it!"

— Hogarth Hughes, The Iron Giant

One of the easiest ways to portray an organism as different from other living creatures is to give it radically different dietary needs. And one of the easiest ways to do that is to have the organism consume metal. Now, while in real life humans and other carbon-based organisms need to consume trace amounts of metals to stay healthy (for example, the iron found in green vegetables is necessary for the production of metalloproteins like hemoglobin), this trope is about creatures that consume pure, refined metal for food. So a person eating the aforementioned green vegetables would not be an example, but a monster eating a steel sword would be.

Such metal-eating creatures often present a unique threat to many of the constituent parts of human civilization compared to other entities with strange diets. After all, automobiles, I-beams, electrical wires, and computers all need metal to manufacture, so a metallivorous monster that devours such objects can throw people's lives into disarray even if the people themselves are unharmed. Heroes can also find it difficult to fight monsters that can eat their weapons and armor. At other times, however, metal-eating organisms can be beneficial to humans, such as by recycling or refining the metals through digesting and expelling them in a way that can be gathered. It's also a common diet for a Nuclear Mutant; radioactive elements such as uranium and plutonium are metals, and irradiated monsters are likely to seek out such substances for a meal. Hard science fiction likes to make these creatures Extremophile Lifeforms, though more fantastical works tend to just depict creatures that resemble those in real life aside from the metal eating.

It is common for the metal eaters to be creatures predominantly made of metal themselves, usually Chrome Champions with some kind of Sculpted Physique. It is also a common trait among robots, in lieu of them needing just electricity and factory-made replacement parts like in real life. A meal for these characters may consist of Palette-Swapped Alien Food with a metallic color and texture, oftentimes with visible seams and rivets to emphasize that it is made from metal. And sometimes, the eater is actually a human or humanlike character who chows down on metal in order to be more "macho".

Subtrope to Fantastic Diet Requirement. Sometimes an example of Extreme Omnivore, unless the character only eats metal. Extreme Omni Goats are very frequently shown eating metal; tin cans, in particular, are a staple item in their diets (though in real life, goats chomping on cans are actually trying to eat the paper labels on the cans). Metal is also a common food for Grey Goo. Compare with Eat Dirt, Cheap, which also deals with characters eating a substance that comes from the ground, and Eating Machine, where metallic robots eat the same food as organic humans. Not to be confused with Tasty Gold or Ate the Spoon, unless the characters really do eat the gold/spoon outright.

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Examples:

Anime & Manga

• Casshern Sins features numerous examples of what would best be described as Robo-cannibalism. The only people still alive are all robots in various forms who all fear the inevitability of death as their metal bodies eventually break down and rust away. Casshern himself is seemingly immortal, and is subject to numerous people who desperately want to eat him in hopes of gaining that immortality. Throughout the series are are many rumors of similar robots who claim to be immortal, and at some point or another meet their end and are ravenously devoured by the hopeless masses.
• Dragon Ball GT: Pan's Robot Buddy, Giru, eats metal and anything made of metal, including the Dragon Radar.
• Eat-Man: The protagonist Bolt Crank has the ability to eat anything and then manifest the consumed objects from his body at will. He especially likes metal, and is often shown snacking on bolts and screws.
• Fairy Tail: Dragon Slayers can, in addition to normal food, consume the element that makes up their magic to quickly restore their magical power and sometimes as a substitute for normal meals. This trope thus comes into play for Gajeel Redfox, the Iron Dragon Slayer, who is often seen eating from a bowl of nuts and bolts during his downtime. At one point he even uses his metal-eating power to help take down a Humongous Mecha.
• One Piece: Wapol is capable of eating metal (among other things..) and even merging with it courtesy of the Baku-Baku no Mi/Munch-Munch Fruit.
• Pokémon the Series: Sun & Moon: Ash's Meltan eats metal.
• The☆Ultraman has a moth-like monster called Goglan who consumes metal while it's in larvae form. It becomes gradually larger after eating enough metal, at which point it grows kaiju-size.
• Ulysses 31: One of the main characters in the series is Nono, a small red robot who likes snacking on nails and always keeps a supply handy.

Comic Books

• In "The Metal-Eaters", a TV Comic featuring characters from Doctor Who, Professor McTurk and his daughter Catriona have created metal-eating insects, and the Doctor has to enlist the help of the latter to save the world.
• Legion of Super-Heroes: Matter-Eater Lad is known for being able to eat anything, up to and including metal.
• Superman:
  • On Silver Age Krypton, there were a race of beasts known as metal-eaters. They were popular attractions at the Kryptonian zoos, with children bringing sacks of scrap metal to feed them. They were kept in their cages with glass bars.
  • "The Super-Duel in Space": Superman meets a Kryptonian, yellow metal-eating mole in the Kandor City Zoo, kept in a glass cage.
  • "The Super Dog from Krypton": Variant. Krypto grabs a crook's gun and starts gnawing it out of curiosity and boredom rather than dietary needs.
  • In The Untold Story of Argo City, Supergirl's family run into one Zygor, a space monster which feeds on asteroid rocks.

Comic Strips

• Redeye: There's a goat that feeds exclusively on metal, preferably tin cans.

Fan Works

• The Ambassador's Son: Dragons, as robust lithovores, are depicted as happily eating metal in addition to their canonical gem-based diet. This serves as a source of humor in one passage where the main character, who has been steadily gaining draconic traits, stumbles home while mostly drunk, mistakes a locked iron gate for candy, and simply eats his way through while thinking to himself that the lead-based paint is a little heady for his liking.
• Changeling Space Program & The Maretian: It's revealed in The Maretian that dragons need to eat some gold for their nutritional needs.
• My Life as a Teenage Von Neumann Device combines this with Wacky Cravings, as Jenny's pregnancy compells her to consume raw materials for her developing baby. Highlights include taking a bite out of Sheldon, popping pennies out of the air like a trained seal, and eating a tub of metal fillings like ice cream.
• Sharing the Night: Spike mentions in the later chapters that he's been cooking a lot with metals like rubidium in lieu of his usual gems because "you can't have dessert all the time". The sequel establishes that metals make up the bulk of the draconic diet — Spike's narration mentions him buying hammerscale as groceries of sort at one point — which makes cohabitation with other species tricky since dragon cooking coats the implements used for it with dangerous levels of heavy metals.

Films — Animation

• In Despicable Me 2, El Macho demonstrates the barbarian power of his new genetically-modified Minions by feeding one an assortment of dangerous metal items, from a chainsaw to a police car to a nuclear bomb.
• The eponymous character of The Iron Giant is an extraterrestrial robot who starts off eating metal objects like TV antennas and the support structures of a power plant. When he starts hiding out at Dean's scrapyard, he eats the old cars and other junk there — though he also eats some of Dean's abstract art pieces that he wasn't supposed to eat.
• In Shark Tale, the Great White Sharks are all shown to be Extreme Omnivores with part of their diet being metallic items, and since Lenny is a "vegetarian shark" that's pretty much all he eats. There is some Truth in Television to this as while sharks don't actually need to consume them, such objects do have a tendency of ending up in their stomach.

Films — Live-Action

• The Adventures of Galgameth: The eponymous Galgameth eats metal, growing larger and stronger with each meal.
• The eponymous character of Pulgasari is a metal-eating monster brought to life from an old blacksmith's clay figurine. As he eats more and more, he grows into a giant Kaiju who helps the peasants revolt against the evil king who had been confiscating their farming and cooking tools to reforge them into weapons. But even after the king is vanquished, Pulgasari is still hungry, forcing the peasants to feed their tools to him instead.
• Ultraman Zearth: Cotton-Pope, the Pet Monstrosity of Alien Benzene, is a gold muncher, who feasts on the contents of a gold mine and, upon depleting the mine, then targets Japan, firstly by consuming most of Kinkaku-ji in Kyoto.

Gamebooks

• Iron-Eaters are amoeba-like monsters from the Fighting Fantasy series and its spin-off The Riddling Reaver. As hinted by the name, they can dissolve iron and alloys for food, including those found on adventurers in the form of weapons and armors, usually by dropping on them by surprise from the ceiling.
• Legend of Zagor have an area where you can gain the assistance of a Parnassian Ironhog, a pig-like creature which feeds solely on metal and rips iron like paper with it's teeth. You encounter it being starved and tortured by an orc guard armed with a wooden spear; after killing the guard and releasing the Ironhog, you can bribe it to follow you by feeding it spare metal parts, at which point the Ironhog will help you attack armoured enemies (including suits of Animated Armor later on) later in the adventure.

Literature

• Age of Fire: The dragons' metal diet is what makes their scales so strong, and failure to include a steady amount of metal in one's diet is equivalent to vitamin deficiencies and leads to weakened and patchy scales. In fact, AuRon is special for averting this, as he is a rare scaleless dragon and so doesn't need to eat any, allowing him to live far from the hominids who mine the stuff.
• The Book of Dragons: In "We Dont Talk About The Dragon", the dragon is kept fed by dropping a bucket of scrap iron in its lair once a week, which at most only ever slightly abates its hunger. In the end, it turns out that it was being fed the wrong metal, as it needed to eat gold instead.
• Book of Imaginary Beings: One variant of the Alicanto bird feeds on gold, while the other feeds on silver. This heavy diet has the side-effect of making it incapable of flight, and it cannot even run with a full belly.
• Dark Lord of Derkholm: A variant appears: the dragons of Wizard Derk's world don't eat gold, but they do have to lie on a mound of golden things, because they absorb essential nutrients from the gold through their skin.
• Galactic Consul: The titular character once gets stranded on an alien planet after an indigenous creature (that appears like thick fog) consumes every metal component of his gear, including his communication device.
• The Heroes of Olympus: Arion is an immortal horse that only eats gold.
• Janitors of the Post-Apocalypse: A Glacidae has a weakness for a salsalike food made with copper.
• Journey to the West: when the Monkey King is finally trapped by Buddha under the five-elemental mountain, the guardians of the mountain are tasked with giving him molten lead as drink and bronze pills as food whenever he's hungry, as part of his punishment.
• Lily Quench: Dragons eat metal, but different sorts are needed for a well-rounded diet. Queen Dragon attacks the factory for iron to eat despite having plenty of gold in her cave because gold is like chocolate to dragons and not as filling as iron. The knights she ate gave her indigestion; she only wanted their metal armor.
• Star Wars Expanded Universe: Balmorran metal parasites, bipedal creatures which live on Balmorra and feed on metal causing sizeable damage to the planet's numerous weapon factories.
• "Wu-Ling's Folly", one of Alan Dean Foster's short stories featuring Mountain Man Mad Amos Malone, put Malone up against a Chinese dragon that needed gold in its diet. Since dragons aren't built for mining, and since it also needed lots of meat, it wasn't exactly a nice creature to have around.

Live-Action TV

• Doctor Who: Pting are a small bipedal species. Although vicious, they are strictly non-carnivorous and cannot consume organic matter. They can consume, however, any inorganic material, including the Thirteenth Doctor's sonic screwdriver, which makes it virtually impossible to contain or confine them.
• In the Farscape episode "Liars, Guns And Money Part 2," the Living Ship Moya ends up suffering an infestation of metal-eating parasites; from what little we see of their feeding habits, they project digestive enzymes onto metal walls and floors, then drink the results. Worse still, these "metalites" arrived on board via the bank container the crew stole in the previous episode and are perfectly disguised as valuable ingots, so nobody recognizes the source of the problem until it's almost too late to save Moya. In the end, the crew are forced to burn the afflicted areas, saving Moya from the parasites but leaving her badly wounded.
• Monster Warriors: In "Attack of the Junk Monster", the Monster of the Week is a giant metal-eating radioactive junk monster: one of Klaus' seemingly failed experiments, but when he threw it out it started absorbing all the metal in the junkyard, becoming a radioactive menace so deadly even Klaus wanted to destroy it.
• Star Trek: The Next Generation episode "Cost of Living". Nitrium is a metal alloy commonly used in Federation starship technology, including the computers, warp drive and life support. The Enterprise is invaded by a parasite that eats nitrium, causing ship systems to fail and endangering the crew.
• Ultra Series:
  • In the original Ultraman, a Monster of the Week named Goldon eats pretty much what the name suggests it does. In fact, Goldon's body is partially made of gold!
  • Pagos from Ultra Q feeds on uranium, giving it atomic abilities. This is also the case with a similar monster named Gabora that appears in Ultraman and Kingsaurus III from Return of Ultraman.
  • The Arindo Ants of Ultraman Taro eat steel and concrete like termites eat through wood, causing structures to collapse.
  • The last monster of Ultraman Taiga, Woola (whose name is a pun on the Chinese phrase 'Wǒ èle', meaning 'I am hungry' spontaneously evolved from space junk, and now feasts on any planet it can get its hands on. It does, however, have a particular affinity to metal, and will prioritise it over other matter with almost as much attention as it gives to raw energy.
  • Grigio Raiden in Ultraman Z needs to consume metal to recharge its Raiden Destroy Cannon. Fittingly, the first place it shows up in after evading STORAGE happens to be right in the middle of a junkyard.

Tabletop Games

• Dungeons & Dragons:
  • The aurumvorax is an eight-legged wolverine-like animal that eats metals and ores, but has a special affinity for gold.
  • Lodestone marauders feed on both flesh and metal; in particular, they need to eat metal in order to grow and strengthen their metallic horns and spiked carapaces. They can live on both ore and pure metal, but find the former less nutritious. Consequently, they are strongly attracted to concentrations of worked metal and are a dangerous pest for civilized races whose armories they like to raid.
  • Rust monsters subsist on rust, which they can create by touching any kind of metal. They corrode metal extremely quickly, enough so that corroding and consuming enemy weapons mid-combat is a very viable combat tactic for them. Planescape reveals via retcon that rust monsters are larval forms of a much more dangerous creature called a rust dragon, which is encountered on Acheron. Their breath weapon can rust and corrode an arsenal's worth of armor in one blast. Fortunately, Acheron is full of scrap metal, but rust dragons crave metal from outside sources the way humans enjoy candy. (A rust dragon who finds itself in Mechanus, a plane made entirely out of gigantic metal gears, is a planar bull in a china shop, and is quickly hunted down by the inhabitants.)
  • Their cousins, the folugubs, can liquefy crystals at a touch and feed on the result.
  • Multiple editions have noted that dragons can eat and metabolize nearly anything if they get hungry enough, expressly including metal; indeed, "some dragons have developed a taste for such fare." Among the different varieties, mercury dragons in particular prefer a diet of metal ore.
  • Steel predators feed on metal, and especially prize metallic magical items. They also inhabit Acheron, giving them a rich supply of food.
  • AD&D 1^st Edition Fiend Folio: The khargra is a monster from the Elemental Plane of Earth. It normally "swims" through solid rock looking for metal ores to consume. If it encounters creatures with metal items (e.g. armor and weapons), it will leap out of the surrounding rock and bite the items in an attempt to eat them.
  • AD&D 2^nd Edition Monstrous Manual: Xarens are stony Elemental Embodiments whose primary diet is metals, unlike their close relatives the Xorn, who prefer unrefined minerals and gems. They're not hostile, but, unfortunately for adventurers, enchanted metals like magical weapons and armour are especially delicious to them.
  • Xorns are creatures from the Elemental Plane of Earth that can smell metals up to twenty feet away. If one encounters Player Characters who are carrying metal (copper, silver, gold and so on), it will demand that they hand over the metal(s) so it can eat them. It will try to take the metals by force if the characters refuse.
  • Dragon magazine #53 "Dragon's Bestiary": The creature known as the argas can improve its armor class by eating certain metals. Iron, mithril and adamantite improve armor class to AC 2, -1 and -3, respectively. Eating silver or gold improves armor class by one or two points, respectively. An argas can receive the benefit from each metal only once, so the best armor class one can have is -6 (after eating adamantite, silver and gold).
• Exalted:
  • Furnace rhinos were created by the Primordial Autochthon to be living refineries for useful metals, and fulfill their purpose by consuming ores and scrap metal, purifying them internally and depositing the resulting materials in their bodies — regular metals make up their hide, while the magical materials form their horns.
  • Steel eaters are earth elementals resembling giant beetles with metallic carapaces. They feed on metal, which they deposit in their shells as they grow until their reach the size of a large elephant. At this point, they form a metallic cocoon where they mature into a steel-winged flying form, which flies off to lay clutches of iron eggs before dying. They were once content to feed on veins of ore deep underground, but in the war-torn times of the setting's present they've taken to digging antlion-like pits to ambush metal-clad soldiers.
  • Ashbreathers are human mutants native to Autochthonia's Pole of Smoke, a toxic, corrosive wasteland that serves as the area where Autochthon's bodily processes dump waste metal for digestion and reabsorption. Among their adaptations, ashbreathers posses sharp fangs capable of tearing through metal, the only food that they can still digest; they can survive by gnawing on the corroded scrap metal that makes up much of their homeland, but prefer to hunt the machine spirits that live throughout Autochthonia — their metal is of much better quality, and infused with vital Essence as well.
  • In Gunstar Autocthonia, the galkak are spaceborne creatures that travel in immense swarms and eat metal. Since Autocthon is primarily made of metal, they're seen as an existential threat to the survival of the fleeing Exalted living inside him and destroyed whenever they're found.
• Magic: The Gathering: Steelfin Whales feed on metal filings suspended in the water, which they filter using magnetic baleen.
• Traveller, Journal Of The Travellers Aid Society #15, article "The Bestiary". Doyle's Eel is a Silicon-Based Life form that eats metal. If it infiltrates a starship it will try to eat metals, silicon and some plastics, which can cause serious damage. It will also try to lay eggs and hatch out more of them, which will cause even more damage.
• Warhammer 40,000: The ferro-beasts of Yimbo-Bim developed the ability to feed directly on iron ore, which it does by melting it into a soup-like substance using acidic secretions from its oral tentacles, to counteract the scarcity of the metal in their homeworld's environment. Concentrations of pure metallic iron, such as those found in most kinds of technology, drive the normally placid beasts into single-minded feeding frenzies.

Toys

• Flick-to-Stick Bungees: The second series, Bionic Bungees, has a character named Kitor who is stated in his bio to gluttonously consume metal without considering if other Bungees will need it.

Video Games

• Cookie Run Squid Ink Cookie, who, when dealing with Power Incontinence, happens to wreck ships and eat any shiny things that spill out, like gold coins.
• Deep Rock Galactic: The reason why Loot Bugs erupt into showers of Gold and Nitra upon dying is that they eat them. If you leave your resources unguarded near a Loot Bug, it will waddle over and eventually eat the raw ore on the floor. Unfortunately for them, any mineral eaten by them gets multiplied by 1.5x, adding even more incentive to kill them. This is also used as the reason why nothing else in the Death World that is Hoxxes IV seems to attack them: Thanks to their diet, most of a Loot Bug's body weight is pure mineral, making them basically inedible.
• JumpStart Adventures 3rd Grade: Mystery Mountain: The Robot Kitchen mini-game requires you to prepare meals for the robot Mort. While some of the ingredients include regular human food, there are also metal ingredients such as gears and gold bullion (and axle grease, presumably so the metallic food can be more easily swallowed).
• KanColle: As this is a game about humanized warships, characters are usually depicted as straight-out eating bauxite, which is one of the resources in the game. Especially Akagi, who is depicted as usually devouring your bauxite supplies.
• Mass Effect: Thresher maws consume underground ore for sustenance, which explains why they can spit acid that melts metal: they have to have that in order to digest their food. It also explains why they attack settlements or military units, as they want to eat the metal structures or vehicles those people have with them.
• Nethack has several metallivorous monsters; with the help of controlled polymorphing, the player character can try out this diet as well.
• Pokémon:
  • Aron and its relatives eat iron, which makes them a nuisance to railroads.
  • Nosepass apparently uses its magnetism to attract its prey to it, which suggests that it eats mineral-based creatures.
  • Meltan dissolves and consumes metal for energy, including other Meltan. While that sounds horrific on paper, it's actually how their life cycle works (in other words, how they grow): Meltan is the baby form of Melmetal, but only the biggest, strongest Meltan of a litter gets the chance. At the end of its natural lifespan, Melmetal breaks up into Meltan and the cycle continues.

Webcomics

• A Beginner's Guide to the End of the Universe: After her third upgrading, Snuffy gains the ability to eat metallic objects and automatically transform them into ammunition for the gun integrated into her body. Chairman Jack is later given the same ability.
• Girl Genius: The Beast is a monster train that eats metals, and then transforms most of it into cars that act as energy reserves.
• Goblins: Klik comes from a race where every member has a "positive" that heals them and a "negative" that hurts them. Klik's positive is metal, meaning it can consume any metal item to heal itself of almost any injury.
• Monsters Can Be Heroes Too!: Coal eats minerals. Lime is also able to eat metal. When the party gets their first quest reward, they have already started eating the coins before Shelly can say they should save some to buy armor and weapons.
• Rusty and Co.: Rusty the Monster Adventurer is a Dungeons & Dragons rust monster — a large insect who eats by dissolving metal with his antennae. He's singleminded to the point of having "Eat [item]?" as a catchphrase, but can put the ability to good use, like eating an attacker's blade mid-swing.
• Step Monster: While Matilda usually eats the same foods as humans, she eats the guns of a pair of would-be store robbers in order to intimidate them.

Web Original

• Neopets: Some food you can give the pets contains metal, such as nuts and bolts. These are said to be palatable but unpopular for most of the pets, except the robots.

Western Animation

• In Ben 10: Alien Force, Big Chill is shown to have a preference for eating metal and anything made of metal, which means almost all of Bellwood city is a giant buffet for him. It's later revealed he has been using said metal he consumes to construct a nest for his babies (he's a Truly Single Parent) and when they hatch the metal serves as an adequate food source for them.
• Darkwing Duck features a race of hat-like alien Puppeteer Parasites that love to eat metal whenever they possess a host.
• In Dexter's Laboratory, the titular character is shown in the episode "A Boy and His Bug" to own a genetically-enhanced termite that eats metal instead of wood, especially the metal scraps left over from when Dee Dee destroys his lab.
• DuckTales (1987): "Attack of the Metal Mites" has Flintheart Glomgold unleash a swarm of bugs called Metal Mites in hopes they can literally consume all the gold in Scrooge's money bin. At one point Gizmoduck attempts to stop them, but the bugs manage to eat the Gizmosuit. The bugs are finally stopped when it turns out they can be restrained by magnets due to all the metal the bugs ate. In the end, Scrooge manages to use the bugs as a way clear out the metal from demolished buildings, and Glomgold ends up having to trying to stop the a few of the bugs from eating his fortune.
• DuckTales (2017): In "What Ever Happened to Della Duck?", Della's spaceship is repeatedly damaged by an arachnid-like Moon Mite. When she confronts the creature, she discovers that it needs the metal from the ship to feed its young.
• The Garfield Show: Subverted in an episode where Garfield gives a goat a tin can so it could lick the glue off it, only for the goat to think he's trying to feed it the can and attack him.
• In Lilo & Stitch: The Series, Experiment 586 (aka. Tank) is designed to eat metal...and grow larger in size each time he feeds. When first introduced, he grows just slightly larger than he was after activating when he eats a small portion of metal, then grows to about the size of a rhino or elephant after eating an entire factory, and then later grows even bigger after eating an immensely large amount of metal afterwards.
• Looney Tunes: In "Drip-Along Daffy", Daffy Duck aims his gun at Nasty Canasta, who responds by biting it in half and chewing it.
  Daffy: Probably didn't get his iron today.
• Muzzy in Gondoland: Muzzy is a green, furry alien who eats metal objects, especially clocks and similar machines. He has a massive appetite for them.
• My Little Pony: Friendship Is Magic: In "Trade Ya!", one of the orthros' heads is seen happily munching on its chain after having snapped it in half.
• The New Adventures of Superman: In "The Iron Eater", Superman battles a shape-shifting alien creature that emerged from a fallen meteorite and devours iron structures.
• Popeye: In The Hungry Goat (1943), the eponymous goat seems to actually prefer metal, cans or otherwise, for its food. Of course, this causes no end of trouble for our hero, whose Navy ship the goat decides to eat. The single, rather small goat simply boards the ship and rapidly consumes anything it can get its teeth on, including an enormous length of chain that just vanishes into negative space.
• Rocky and Bullwinkle: In one story arc, our heroes are menaced by Metal Munching Moon Mice, large robotic rodents sent by Boris to eat the nation's TV antennas.
• Samurai Jack: In the second segment of the episode "Jack Tales", Jack meets a family who expresses desire to eat his sword. Upon fighting them, he slices the face of one of them revealing them to be robots. Once their own metal is exposed, they start eating each other.
• She-Ra and the Princesses of Power: Played With in "Princess Scorpia", when Scorpia sets out a dog bowl of nuts and bolts for Entrapta's robot, Emily. She's "still not sure" if it actually eats.
• The Simpsons:
  • Subverted when the family goes to a petting zoo. Homer tries to get a goat to eat a tin can and it won't do it.
  • There's two-headed crime-solving goat. One head eats tin cans and the other eats health food.
  • "Eight Misbehavin'": The family goes to an Ikea-like store and runs into their mascot Allen Wrench, who is shaped like an Allen wrench. It turns out that Allen Wrench is really an alien who was enslaved by the store and lives off of tungsten, which he confides to the family.
    Robotic voice: I need tungsten to live! Tungsten!
• Street Sharks: Due to being able to eat just about anything, the Street Sharks are able to consume metal with zero indigestion involved.
• Superman: The Animated Series: During Superman's first fight with Lobo in "The Main Man — Part 1", Lois Lane tries to help the downed hero by striking Lobo with a lead pipe. Lobo is unfazed by the attack, then grabs the pipe and eats the whole thing with comical speed.
• Teenage Mutant Ninja Turtles (1987): A dinosaur-like creature from Dimension X called a Zipp has an endless appetite for metal. Even worse, eating copper makes it multiply. Eating chocolate re-merges them into one, but into a giant Zipp. The only way to make a Zipp vanish and/or shrink is for it to eat an extremely rare metal called Regidium.
• Transformers:
  • The scraplets are mechanical parasites that transform between a humanoid form and nuts and bolts. They appear in The Transformers (Marvel) and the Transformers: Prime cartoon.
  • Unicron, from various continuities and media of the franchise, is a mechanical planet able to transform into a humanoid robot. He is a Planet Eater who devours other mechanical planets and its robotic humanoid inhabitants.
  • The Dinobots fed on the robotic aquatic wildlife of Cybertron in "Grimlock's New Brain", with Slag stating it was a regular thing they did. Grimlock's bio stated that he would eat hapless Decepticons he defeated and in the 1986 movie famously declared "Me, Grimlock, want to munch metal!" when confronting the Sharkticon horde. Several Decepticons also devoured metal and unfortunate Autobots, including the Terrorcons Hun-Gurrr and Sinnertwin.

Real Life

• There are certain extremophile single-cell organisms that feed directly on metal. Among them are:
  • Halomonas titanicae is a deep sea bacteria that feeds on iron. It was so named because it was found to be the source of the "rusticles" forming on the wreck of the RMS Titanic.
  • The Cupriavidus metallidurans is able to eat toxic forms of gold and turn them into inert nuggets.
• Because gold is usually a non-reactive element (as well as soft enough to bite without it damaging teeth, hence the Tasty Gold trope), it is safe for humans to consume and has occasionally been incorporated into food and drink for millennia. But the non-reactivity also means that it has no nutritional value or flavor either, so any chefs who put gold into/onto their dishes do so only for the visual aesthetics and/or Conspicuous Consumption as part of Snooty Haute Cuisine.
• Technically speaking, everyone eats trace amounts of metal—the iron statistic in dietary information really is referring to the same compound as the metal, and a sufficient iron intake is considered a requirement for life as we know it.
• Michel Lotito (otherwise known as "Monsieur Mangetout" or "Mr. Eat-All") had pica disorder, as well as a thicker stomach lining and stronger stomach acid that allowed him to easily digest the metal he ate.

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