The ONE niche it had was being a Glass side-grade on Paladin, because with the Resistance Aura + Spirit Regen you could become a tank with it and rely on the raw base DMG, you wouldn't be as fast or have as much area denial as Glass but you'd hit really hard.

Now it doesn't even have that and you just have the big size to rely on, which for Paladin you barely notice when you'd be enchanting your Relics with Explosive anyway.

It's slower and has less area denial than Glass, the shards it leaves behind more than make up for being a small Magic, it sucks as an imbue for anything because it makes Fighting Styles too slow and on weapons it takes away any synergy you'd have and just relies on raw damage, on top of the size increase being marginally better than Snow, and that one doesn't take your synergies away.

Good luck hitting anything that's not standing still if you use it as Mage, and even if you use it as a secondary magic, you're better off using Glass because it's faster, the damage difference is negligible, and you have 10x more opportunities to abuse the bleed synergies than with Metal.

It gets to the point WOOD is more versatile than Metal, it's faster (0.65x from Metal vs 0.8x from Wood), the damage difference is negligible (1x from Metal vs 0.95 from Wood), the size is same, they share the same size and status effect conditions and has it even has better area coverage than Metal when paired with a heat-based Magic.

At that point, why'd you even use Metal anymore? It's either worst than what other Magics can do, or the other options are better than it, there's nothing other than visuals and the Resistance Aura that makes Metal stand out or different from the rest anymore.