I like Citadel's (or Warhammer's, as they are to rebrand) Retributor Armour with a shade of Carroburg Crimson and a highlight with Vallejo's Polished Gold.

I've been using Two Thin Coats brand paints. I like how thin and workable their gold ('Glistening Gold') is straight out of the bottle while also having good coverage.

For my cars if I want true metallic I use enamel metals from testor. I find the best way to make a metal stand out is to make sure the base color is complimentary or contrasts effectively. A brown under a gunmetal makes for good rough metal iron look. Black under steel makes a deep base for the steel to shine over. Etc.