What kind of metallic are you looking for?
-Like metallic (flake) paint? In that case I'd just use a strong red, and add a metallic medium, like Vallejo make. If it turns too pink, just add a drop or 2 of red ink.
-A deep, metallic, lacquered red, like on, for example, custom sportscars? Those are known as Candy Colors, Candy Coats or Kandy Kolors.
Several modellers have found ways of reproducing these, just google them.
Most are variations of what Vikotnik describes.
But instead of an ink glaze, most use multiple layers of gloss varnish or lacquer, tinted with ink or food colouring.
HERE is an example of the technique (bottom article and the Griffon Sports article). If you use regular (wargames) paints for the metal layer, you get something that still looks like flake paint. Use something that gives a smooth coat, like Alclad, and you get that smooth, even metallic sheen.
The fun thing is, as long as you have the corresponding ink, you can do a
lot of colours...