What is the strongest metal in the DC universe?

Question

Vibranium/Adamantium are two of the most powerful metals in the Marvel universe. Similarly, what is the strongest metal in the DC universe? Answers from the comics, animated and live-action movies/shows are acceptable.

Answer 1

Superman (in World's Finest #41) creates a new element by applying heat and pressure to an ore. It's named Supermanium in his honour and is described as 'the hardest substance in existence'.

This is backed up in Superman #167, where it's described by Brainiac (who's pretty smart) as 'the strongest metal known to science'.

Interestingly, in Superman #365, Superman himself describes it as the 'densest' metal known, so it's apparently both the densest and strongest.

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Honourable mention #1 goes to Amazonium, also described by Diana (in Wonder Woman #52) as the 'hardest metal known'.

and by the narrator in similarly glowing terms in Wonder Woman #68.

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Honourable mention #2 goes to Marvelium, created by Captain Marvel in Captain Marvel Adventures #100. Much like Supermanium, it's created by crushing other elements to make the 'heaviest and strongest element of all'.

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Honourable(ish) mention #3 goes to Inertron, a metal created by Brainiac 5 in Adventure Comics #336 that is supposedly "the most indestructible substance in the galaxy". It loses points because it gets destructed repeatedly, by Karate Kid, Superboy, Element Lad, Mon-El and various others over the next few decades.

Answer 2

There are several metals which have been described as unbreakable, indestructible, or the hardest or strongest in the DCU at one time or another.

As noted in Valorum's answer, you have Supermanium, Amazonium, Marvelium, and Inertron (a metal newly-discovered in the 30th century), all of which existed in the Pre-Crisis era of DC comics.

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Additionally, Promethium was introduced late in the Pre-Crisis era, but also exists in the later Post-Crisis continuity, and the current Prime Earth continuity as well.

VERNON QUESTOR: Promethium-coated metal... creating a virtually indestructible car to eliminate accidents.

_{New Teen Titans Vol. 1 #9 (July, 1981)}

In a DC/Marvel crossover series, Promethium was cited as a DCU counterpart to Adamantium.

ACCESS: Whoa--nice job! Wonderful, even! And that's one tough length of lariat you got there! What is it--Adamantium?

WONDER WOMAN: Enchanted. I've never head of this--Adamantium.

ACCESS: Indestructible metal. Doesn't exist in your universe--but you've got Promethium, so it kind of evens out.

_{Unlimited Access #1 (December, 1997)}

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In the Post-Crisis continuity, the term 'Amazonium' wasn't in use, and Wonder Woman's bracelets were simply said to have been created from the remains of Zeus' Aegis shield, formed from the hide of the Great Goat Amaltheia.

POSEIDON: Those trinkets were once part of Zeus' mighty Aegis itself... the impenetrable shield formed from the hide of the Great Goat Amaltheia, who wet-nursed the infant Zeus and thus provided the energy from which Olympus sprung. Only two beings were ever able to violate the power of the Aegis.

ZEUS: Aye, it was our father, Cronus who splintered the shield as he smote it with his final blow. When I bequeathed the shield to my daughter, Athena, she, unbeknownst to me, had Hephaestus reforge the loose fragments... into a great prize to be awarded to the mightiest and worthiest of all her Amazons. And it was Ares who long ago demolished the Aegis. Your bracelets are all that remain of that.

_{Wonder Woman Vol. 2 #21 (October, 1988)}

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In the current Prime Earth continuity, Kerenthium Steel was purported to be the strongest metal in the universe, but was broken by Superman.

Your chains were forged under the pressure of an inverted black hole. The only way to manipulate Kerenthium Steel -- the strongest metal in the universe. These chains are used to haul stars between galaxies.

_{Superman: Up in the Sky #6 (February, 2020)}