Vallejo model air has a very good line of airbrush metallic color. It came pre thin, but I prefer to thin it a bit more with vallejo airbrush thinner. You can find bunch of reviews of those metallic color on YouTube.
Vallejo does clog the needle tip after ~20 seconds(you can tell by the outflow decreasing), but it is easy to clean with a q-tip + alcohol on the tip. May be this will fix your clogging problem, unless the clog happens on other places.
Another way to avoid clogging, if your airbrush is dual action, release the paint first then the air, so the air will shoot out the residue paint in the needle. Do the same when you start airbrushing, pull down for air first, then press down for color.
I usually thin my own paint in the airbrush, then back flow to mix the paint. Or use those tiny disposable measurement cup for medicine.
If you don't mind lacquer paint, there are also Allclad II, just get a mask so you don't get brain damage.
What kind of paint are you using?