Living metal

The living metal from which Transformers are constructed is known by many names, including protomatter, sentio metallico, birth metal, cyber-matter, elemental metal, and Transformium. Often depicted as the living stuff of Cybertron itself, it is no ordinary metal, possessing a self-replicating cellular structure and a genetic code that, together with a spark, defines and shapes a Transformer's natural alternate mode. This adaptable matter is also capable of being programmed to reconfigure into new shapes and designs, which is what allows a Transformer to change their alternate mode when they desire. Both this living metal and sparks themselves are, at the base level, composed of Rarified Energon.

It is entirely possible for a new Transformer body to be built without using this elemental substance, using only regular metals; the resultant being is no less of a "real" Cybertronian, but may face some social stigma in an unenlightened society. In some universes, the infusion of a spark into such a body will actually convert it into living metal.

Fiction

Japanese Generation 1 continuity

Being made out of living metal is what makes you a "super-robot lifeform," instead of just a regular ol' robot! When a Transformer dies, their living metal becomes drained of color, leaving their remains various shades of grey The Transformers: The Movie Birth of the Fantastic Double Prime Ginrai Dies!! or stark white. Call of the Primitives The Mystery of Planet Master

The Pretenders were able to convert their living metal into organic matter to disguise themselves as human beings. The Master-Braces used by Headmaster Juniors and Godmasters were capable of achieving the opposite effect, temporarily converting the organic cells of human tissue into metal, thereby allowing the humans to transform and combine with Transtectors. Super-God Masterforce

The Decepticon Emperor of Destruction Deathsaurus wielded the Living-Metal-Destroying Cannon, a powerful weapon that fired energy blasts which killed the cells of living metal. Resurrection!? The Decepticon Fortress However, the cannon had no effect on the Autobot Victory Leo, as his body was made from the rare and powerful energy ore gurunium. The Strongest Partners, the Combination of Victory!

Marvel Generation 2 comic

Afforded a glimpse of the birth of the Transformer race, Optimus Prime watched as the first Cybertronian emerged from the fabric of Cybertron itself, their raw body a mass of liquid metal over an endoskeleton that promptly took shape and color as a crackle of light traversed its shifting surface. As the vision continued, Optimus saw how Cybertronians had once multiplied: the living metal of their bodies replicating and dividing like a cell, forming a huge liquid metal pustule on the robot's body, which then burst to release a new, raw Cybertronian body that quickly took form. The Power and the Glory

Animated

Cybertronian life begins with protomatter, which is mined from Cybertron's Sonic Canyons and crafted into protoforms, which are then brought to life by the infusion of a spark from the AllSpark or Vector Sigma. The AllSpark Almanac II

IDW Generation 1 comics

Now to be fair, this is actually a cloud of scraplets posing as a protoform in its rawest state, but if they're good enough to fool Swerve, they're good enough for TFWiki!

A "natural" Transformer birth results from a spark igniting in a region of Cybertron (or one of its moons) known as a hot spot. The ignition of a natural-born spark is accompanied by the formation of a portion of birth metal—scientifically known as sentio metallico—around it, which is harvested from the planetary surface along with the spark in a specific quantity determined by an equation. The Fecund Moon Silent Light The sentio metallico will quickly coalesce around the spark to form a protoform, which in a short span of time will take on its natural shape, growing limbs, facial features, and manifesting its natural alternate mode, throughout which it will remain warm to the touch. Silent Light Occasionally, however, the sentio metallico may have difficulty reading the genetic "instructions" of the spark, and struggle to assume its natural form. In such instances, a Cybertronian obstetrician known as a blacksmith will help nurture the protoform and sculpt it into its "god-given" shape. A World Misplaced

If a spark is not harvested from its hot spot and left to fade out, the sentio metallico typically dies with it. In incredibly rare instances, however, it will survive as "widowed metal," re-patterning itself into a snowflake-shaped bloom of incredible valuable. A World Misplaced

Such naturally-born Transformers are called "Forged." The Fecund Moon By contrast, "Constructed Cold" Transformers are ones whose bodies were built in factories from conventional materials and implanted with sparks, and were for a time considered "lesser" than Forged 'bots, resulting in social apartheid. The Divided Self Chaos Theory, Part 1 It is possible to use sentio metallico harvested from other sources to built a Constructed Cold body, however; this was the tack taken by the Decepticons at Grindcore Prison, where they smelted down the bodies of prisoners to harvest raw materials to build a better class of M.T.O. Speak, Memory! (Part 2)

The remains of extremely old Transformers, such as Censere, dissolve into inert sentio metallico—a reddish powder—shortly after their demise. The Sun in Flight

Aligned continuity

The living substance of Cybertron is known as cyber-matter. When Megatron poisoned the core of Cybertron with Dark Energon during the war, the planet lost its ability to sustain life, which could only be restored by an infusion of fresh, living cyber-matter. The Omega Lock appeared to be the only source of such a power, but when it fell into Decepticon hands, Optimus Prime was forced to destroy it to prevent it being used to cyberform Earth instead. Though Prime was successful, Megatron still managed to use the cyber-matter to create a fortress for himself in Nevada before the Lock was destroyed. Darkest Hour

Salvation for Cybertron manifested from an unexpected source when the genetic material of some failed clone Predacons was inadvertently mixed with Synthetic Energon during an explosion in Shockwave's Project Predacon laboratory. The blending of the two materials resulted in an unstable form of cyber-matter, which Megatron tasked Shockwave with perfecting, planning to use it and a reconstructed Omega Lock to cyberform Earth and Cybertron. To this end, the Decepticons kidnapped Ratchet, from whom they had obtained the original formula for Synthetic Energon. Minus One Persuasion The formula was completed despite Ratchet's attempt at destroying it, and the cyber-matter was loaded into the newly-constructed Omega Lock. This led to a battle with the Autobots on board the Nemesis, during which Bumblebee was fatally injured and fell into the Omega Lock. Immersion in the primordial soup of Cybertron healed Bumblebee's wounds, including his long-damaged voicebox, and he subsequently emerged to kill Megatron.

With the Decepticons defeated, Team Prime took the Nemesis to Cybertron. The quantity of cyber-matter they possessed was not enough to manually restore the entire planet, and as Ratchet did not know Shockwave's half of the formula, they were unable to create more, but Optimus Prime had the solution: he launched the cyber-matter into Well of All Sparks, where it revitalized the core itself, so that it in turn could restore life to Cybertron. Deadlock

Live-action film series

The elemental metals used to forge the bodies of the Transformers were created by an alien race known as the Creators. These beings used cyberforming "seeds" to converted the organic material of other planets into living metal that they then harvested and took to Cybertron, where life was breathed into it using the AllSpark. Prehistoric Earth was one of the worlds where the metals were generated, and the deployment of the seeds there triggered the Cretaceous–Paleogene extinction event, wiping out the planet's dinosaurs and even converting some of their remains into metallic skeletons.

Kre-O Bayformerized.

Small deposits of the metal were left on Earth which survived into the modern day, but humanity could find no use for the mysterious substance, unaware of the true power it held. It was the arrival of the Transformers on Earth that allowed Kinetic Solutions Incorporated to make the connection between the mysterious metal and the physiology of the aliens. The Battle of Chicago gave the company the chance to obtain the remains of multiple deceased Transformers, and using their remains, KSI proceeded to crack the Transformer "genome", and learned how to program and manipulate the metal, to which they gave the commercially charged name "Transformium". Using Transformium, KSI began developing man-made Transformer prototypes, including the Bumblebee "knockoff", Stinger, and the centerpiece of their line, Galvatron—robots that exploited the reconfigurable properties of the metal to "transform" in their own unique way by exploding into a cloud of Transformium particles and reforming in alternate mode.

With Earth's limited supplies of Transformium dwindling in the face of their escalating production, KSI head Joshua Joyce wound up conspiring with CIA agent and anti-Transformer fanatic Harold Attinger, who provided Joyce with an additional Transformium supply in the form of the dead bodies of Decepticons that his Cemetery Wind task force rounded up (though unbeknownst to KSI, many of those corpses were in fact Autobots). Even this was not enough, however, but Attinger's secret ally Lockdown promised salvation in the form of a cyberforming seed that could provide them a vast quantity of Transformium for decades in exchange for assistance in capturing Optimus Prime for his own ends. They intended to safely detonate the seed in the Mongolian desert, creating enough Transformium to last for decades, but Galvatron—in actuality, Megatron reborn through silent manipulation of the KSI and its Transformium—sought to obtain it for himself, and had no such compunctions about protecting humanity from its effects. He took control of KSI's small army of Transformium prototypes, but his plan was foiled by Optimus Prime's Autobots and their human allies. Age of Extinction

Ask Vector Prime

When questioned on the subject, Vector Prime observed that the various names used across the multiverse to refer to the living metal of Transformers' bodies, including "protomatter," "cyber-matter," and "sentio metallico" were all different names for the same thing (but also noted that an expert might potentially distinguish subtle differences between them based on the differing physical laws of different universes). He was loathe to use the word "Transformium," to refer to it, but only because he feared legal reprisal for infringing on a KSI trademark. In response to further questioning, Vector also explained that, in some universes, the infusion of a spark into a body made with conventional materials could convert the substance of that body into living metal. Ask Vector Prime 08/03/15

Notes

• The term "sentio metallico" was created by writer James Roberts for his unofficial Transformers novel Eugenesis, to refer to the living metallic stuff of Cybertron from which Transformers were birthed in the Generation 2 comic. He would later introduce the term into canon through the IDW comic books, in which it was established to be the substance which makes up protoforms.
• The word "protomatter" was first used in Transformers fiction to describe the watery-looking substance that makes up transwarp portals in the 2000 prose story "Schism." This usage would never be repeated, and its subsequent use as the name of the matter protoforms are made out of—in Beast Wars: The Gathering, The AllSpark Almanac II, and Ask Vector Prime—was not likely a deliberately repurposing of this word, but just a coincidence.

See also

• Technomatter, a term used exclusively to refer to organic material converted into metal.
• Sentient metal, an Earth-made material created by NASA from which the Autobot Pepsi Convoy is constructed.