Finetec/Coliro will continue to be a perennial favorite for all the reasons described above, and they are my go-to metalics. But just to add a little variety to the discussion, I'm going to throw in for Yasutomo pan gold. It comes in a darker/warmer gold and a lighter/cooler gold (pictured), and also a silver. The porcelain pans are luxurious and enormous and reusable for mixing other paints when/if you ever finish using up one. The pigments are ground very very fine - much finer than Finetec or the Dr. Ph. Martin's metallics (that come as a liquid with an eyedropper lid, and which I use a lot because I'm a huge fan of the "nickel" color). You have to add a drop of gum arabic to get them to stick to the paper, which makes them a little more persnickety to use than Finetec, and they don't look super special....until you burnish them! and they will shine like real gold leaf.
--yours, K