Do you need to use a color preserver when you use metallic thread?

No. Metallic is not ideal for guide wraps though. The tension required can strip off the metallic coating. It can be done but IMO metallic is better left as trim. 

CP is not necessary on metallic thread, but it doesn't hurt it either. It's nearly impossible to apply CP to your guide wraps without getting some on your metallic trim bands. Don't worry about that. It won't hurt anything.

 

DVT is correct about using metallic for primary guide wrapping. It's not ideal at all. If you're going to do it, you'll need to be very precise, and very careful. The coating comes off easily.

I was just going to use it for trim bands and a little bit in the center of the wrap (whatever that is called). In think I'm going to use colorfast thread for my "main wrap" so I won't have to use color preserver at all.

Don't use CP on just part of a wrap or you'll get blotches. Even NCP thread is not 100% impervious to CP.