It is presently very fashionable to not use any metallic paints when painting metal surfaces on miniatures.  Base colors are blended from dark to light to achieve a "metal" effect artistically rather than relying on the easier technique of using metallic paints.

The picture to the left illustrates that with practice, metallic painted can be stained and blended to achieve a very high-quality chromed effect.

The figures are the old Terminator Endoskeletons from the now-defunct Leading Edge Games.