When you have the Icarus Armor, go to Noah's Park stage again with Pallete as navigator. When you get to the room where she says "Find a way to break those rocks above you", jump up and hit the rocks with the Icarus Armor. Up there is a Rare Metal.

Have Zero and somebody else, and Alia as navigator. At the first waterfall she will say there is a ledge that you can jump up to. That is where the Rare Metal is located.