So an important question. Can powdercoat be metallic? Never thought there was such a thing.
Yes. But talk with your powdercoater you are going to use first -- some do industrial (one color) whereas others are into the funky colors, overlays, metallics, etc. Make sure they have done it before!
I've seen some four process PC done in the past. Base coat, metallic, toner (fade) and then clear. Really thick looking though -- so make sure you like that look.
For most factory Ducati frames, I usually do the following: tinted base/primer (heavier to fill the welds) followed by the final PC color itself.
I've also taken frames from the PC AFTER the first thick base/primer and then brought them back to shop and wet sanded to blend things better. Cleanup and bring back and let them do final PC coat. A bunch of SoCal custom car builders do this trick on chassis as it blends welds for showcars quickly and without much labor. Some just paint over the PC itself if they can't get the right color PC mixed.
Also you can get "color matched" PC colors made. Just bring a sample and they can route back to Cardinal or other supplier and get made. I think it was $35/extra last time to get color matched PC mixed. I've had very good luck in matching solid colors.