Black metal feels like a nice breakpoint to get a ton of gear and upgrade your bases. I feel like I focus more on base building and gearing up once I set up in the plains more than in previous biomes. I bronze and iron I normally save up for later, and silver isn't used to make "base" gear. Once I get black metal, I start to really upgrade things like pickaxes, axes hoes, storage chests, etc and get to work on building. Would be cool to get armor from it too though, but it has a pretty unique function in the game that impacts QoL.
