How far are you willing to go? Vallejo’s “Liquid Gold” range of paints (which also includes silvery metals, despite the name) is a favourite among many top-tier painters in the mainly non-historical scene, for the superior metallic effect. However, these paints are alcohol-based and the (real metallic) pigments would rust in water. I’ve been tempted to try these paints as I’d love to have a broader range of shininess-dullness to play with when painting metals, but so far my reluctance to deal with the extra hassle and the risk of accidental oxidation has won out. I can’t recommend what I’ve been too cowardly to try myself 🙂
Vallejo also has something it calls the “Metal Colour” range. It’s water-based but stands apart from the “regular” metallic paints in the Model Colour and Game Colour ranges. It’s mainly made for airbrushing, but can also be applied with a brush. I’ve heard some accounts that even when brushed on, it’s a bit shinier than other water-based metallic miniatures paints. I’m not sure whether that’s really true, and even if it is, the difference might be marginal. I meant to try these paints once but accidentally bought the wrong ones. Vallejo has so many different ranges of paints, it gets confusing.