you will have much better results if you can sandwich the metal. Metal bends and catches the blade going up and down. If you are worried about overall thickness, use 1/8" plywood, otherwise I like 1/4" better for stability. I cut aluminum frequently for jewelry I also use some steel. Other nicer metals are fun but get more expensive to play with. I have a couple of jewelry supply sources at home, I know you can get a variety of types of metals in small sheets for metalworking jewelry projects. I won't be home for a few days, but I'll look into a source. Some craft stores have a small selection of metal options. Are you looking for a silivery metal? Are each of the elements cut out individually and stuck together, or from one piece?
I personally prefere wood jewelry, and make alot of it. Is the a reason wood won't work?