Wow, didn't expect this to take off like it did , or go down this turn. Well, the point I was trying to make and I kind of agree with GM4Him, is that with a little imagination, yes, you can have medium armors that are not made of metal. Perhaps they need to be specially made (hint, hint, HINT!!!! Crafting! :D), or purchased at specific vendors, and perhaps only available to Druids.(just as some other armor would be available only to other classes, like the Githyanki armor). I've always seen it as Druids can use some metals, mainly the pure ones, iron, gold, silver, etc. Hell, some sickles are made from electrum, which is gold and silver mix (representing the sun and moon combined). Steel is the problem because it is essentially processed and combined with other ores, so it wouldn't be considered "pure" any longer. Just my opinion though.
