I have found that the best way to use metallic when FMQ is doing bobbin work.
Load the machine with water soluble thread on the top and bobbin. Place the item on the machine face up. Stitch around the perimeter of the area you want to embroider. If you wish you can do a mock embroidery of what you want where you want it. Remove the water soluble thread from the top AND bobbin and keep in a safe place (the results may be horrible if you don't keep it safe). I like Superior Metallic Thread. Load the metallic on the bobbin, and a very fine thread, like The Bottom Line on the top. Turn the item upside down and do your embroidery or FMQ. Wet the item to dissolve the water soluble thread. When you load the more delicate threads on the bobbin they are subjected to very few points of pressure, therefore it doesn't break.
Good luck with your project.