The monsters of this archetype are based on the anime Megazone 23 and Genesis Climber MOSPEADA, the latter of which has been adapted into Robotech. The Fusion Monsters resemble the Pendulum Monsters' vehicles transformed into power suits, as depicted in "Metalfoes Fusion" and seen with "Goldriver" and "Orichalc", the latter of which resembles the MOSPEADA unit in its battle form. Other "Metalfoes" members are based off other popular media such as Akira and Fullmetal Alchemist.
"Metalphosis" is a portmanteau of "Metal" and "Metamorphosis". While the Pendulum Monsters of this archetype are named after real life metals/alloy, the mythical and legendary metals/alloy are used for Fusion Monsters.
The Main Deck "Metalfoes" monsters are comprised of Normal Pendulum Monsters, except for the EffectPendulum Monster "Raremetalfoes Bismugear", that all have the Pendulum Effect to destroy one of the player's own cards and Set a "Metalfoes" Spell or Trap Card from the Deck simultaneously. Their playstyle is similar to the "Igknight" archetype, which is also FIRE Pendulum-based deck with tendencies of destroying each other to search one another. Because they can destroy any face-up card to have their effects running, they are largely viable to be used with several cards or archetypes that benefit from destruction such as "Yang Zing" in order to generate multiple advantage in rapid succession.
Aside from Pendulum Summoning, this archetype can Fusion Summon with "Metalfoes Fusion", which can easily return itself to the Deck for a free draw; it can then can be searched out again with the Pendulum "Metalfoes" monsters to repeat the process. "Metalfoes Combination" can be used with "Painful Decision" to gain more field advantage from Fusion Summons while also recovers those spent monsters. Furthermore, most "Metalfoes" Fusion Monsters require completely generic materials - further emphasizing their splashability and capacity for mixing with other Decks with little problem. Mixing in other Pendulum archetypes can allow for powerful field presence, using Pendulum Monsters as materials from the field, and Pendulum Summoning those materials back from the Extra Deck later.
Since "Metalfoes" is a Pendulum-based deck, cards that prevents Special Summons such as "Vanity's Emptiness" and "Vanity's Fiend" can slow their progress. "Anti-Spell Fragrance" can also prevents them from activating any of their Pendulum Effects, along with slowing down their Fusion strategy.
Since their Pendulum Effects revolves around destroying cards in order Set their Spell/Traps, "Magical Spring" can be surprisingly effective against this deck, preventing them from destroying any of their cards in Pendulum Zones, potentially halting them for the entire turn.
Banishment effects also works well against this deck, specifically against this deck's "Metalfoes Fusion" to prevent it from recycling itself (since most players only play one copy at most anyways).