I use Superior's metallic threads with great success. I have Bottom Line in the bobbin, and as recommended by them, a Topstitch 90/14 needle.
A couple of tips I picked up also:
Have the thread lying on its side in an open container behind the machine (i.e. not upright on the machine thread holder), then thread the machine, but do not put the thread around the very last bar on the needle holder, bring it down from the guide after the tension disc directly to the eye of the needle.
You need to use a lower speed with metallics, especially with free motion. This was my first fmq with Superior gold metallic.