>but it would be interesting to ponder how they would have evolved on a metal planet
It overlaps a whole lot with the concept of a dyson trees, but the core problem is that it needs to be able to use the metal in the first place - earth is a metal planet, in the sense that ~10% of the planet is iron, and yet our trees are not steel.
I don't really think that's a fair assessment, since most of it is in the core. That's some very long and heat resistant roots.
I also can't help but wonder, could trees even use iron if it was plentiful in the upper crust? You need a lot of energy to separate iron oxide into elemental iron. Betting against what evolution can make is usually a bad idea, but that would be a neat trick.
It overlaps a whole lot with the concept of a dyson trees, but the core problem is that it needs to be able to use the metal in the first place - earth is a metal planet, in the sense that ~10% of the planet is iron, and yet our trees are not steel.