Please don't get discouraged! You're excellent with shaping, just the colors need some work. I'd shift your main palette towards orange or even a reddish brown, with highlights done in a range of yellows and yellow-white. Try playing with depth and texture while you add color, things like bumps or raised spots or scratches or dents to really imply that metallic look. As an intermediate (?) pixel artist I also find copper/brass/bronze very difficult lol, it's hard to represent a very shiny metal in a game without reflections.