I'm guessing by "metallic" that you mean "metal flake"? The bigger the flakes of metal, the more difficult it is to spray and the more expensive it is to have done. You won't find much in a spray can because the nozzle is too small to allow the flake to pass through it. There is a product by Duplicolor called "Metal Specks" that comes in a clear paint with silver specks, that can be applied over any color to give a metal flake look. It also comes in a few other colors.
If you're talking actual "metallic" paint, you can find some colors at your hardware or auto parts stores, Home Depot etc. You can use a metallic silver and spray over it with a blue clear to get a blue metallic. Their are a bunch of different combinations just in cheap Walmart/Home Depot paints you can try out. Go crazy.
For crazing with Killer Cans Crazer you lay down the paint and then apply a texture to it. It creates a marbling effect. You can use cling wrap, sponges, anything with a pattern and apply it to the wet paint, causing it to marble in the patterns you have made. Very cool stuff.