I say "Composition" because I'm not talking about how to paint metal so much as how to create contrast by balancing painting techniques across a miniature.See, when I began painting Non-Metallic Metals, I found that despite its pleasing tones, metal can end up looking flat and dull. You're painting with the same colours used on the rest of your model so everything blends together. Since I'm a big fan of using contrast to make a model visually "pop", when I'm painting with NMM, I'll usually throw splashes of True-Metallic Metal on smaller details like bolts, rivets, buckles, etc.
As an example, take a look at the orange terminator here. Since everything is painted with regular paint, it all has a similar appearance. But, I used some colour variation - the orange is very strong and stands out boldly while the lighter colours like the cloth and golds are softer instead. The black metal parts are bold and strong too, but your eyes are probably treating them similarly to how they look at the orange.
I'm going to preface this by reminding people that I'm self-taught when it comes to art. This article is mostly theory and I'm talking about how things appear to me.
