Here\'s my 2 cents:
Copper is used to make bronze. Copper is out. Bronze is in.
Steel. Steel is just a very good example of smithing material and should be used as armor, weaponry, etc. Steel is in.
Gold is not an armor. If I had a dime for every time that gold made a good example of an armor, I\'d be broke. Gold is out. And SteelGold is out.
Silver is a mineral I think. Silver is half in and half out.
Platinum would be good for rings and amulets and necklaces, but not as an armor. Do you want to be glistening like a beautiful white swan the moment before you decapitate the ultimate evil? I think not. Platinum is out.
Also using things like SilverPlatinum and SteelGold are just prolonging the levels to get somewhere. No double metals like that, because in the end its just stupid.
If I had a say in this I would say Tin (I believe Tin is a mineral yet can be used by iteself as an armor like the Tin Man in Oz), Bronze, Steel, and now that I think of it, Silver.
We don\'t need billions of metals. And you know there is gonnna either be a hacker or some guy with plenty of coffee, or some sort of macro and will mine, mine, smith, smith until the cows come home. This player will own the monopoly, charge extremely high prices, and be the BlueRose13x of PlaneShift. But with three kinds of metal, and making it so you can only get to a bronze sword, that makes other things more interesting. You could trade, or go on a \"blood run\" against a hord of enemies and attempt to get one.
There could also be other metals, not usable by players, that the dwarves use to make special sword only attainable in tasks made by them, or traveling long and far and knowing the password to the dungeons of Rordyar and sneaking pass the goblins who have their bows aimed at your head at all times.