Mind thy language, pilgrim, or the forum polizei will stomp you.
Airbrushing is 50% science, 50% engineering, and 50% art. Just do the math…
The consistency of 2% milk would be better. Whole milk is a little on the thick side. You also didn't specify type of airbrush (gravity or siphon feed), distance from brush to model surface, or the pressure you are using.
For properly thinned paint, about 10 to 15 psi is right for a gravity fed brush. For a siphon feed, 15 to 20 psi. Drop the pressure to the bottom of the range for fine work. You will generally get better results by dropping the pressure and getting closer, but this is a matter of practice and "feel"—this is where the art comes in. You have to find the right combination of dilution ratio, pressure, and distance. This will vary somewhat from one paint to another, with humidity and temperature, and the way you are holding your mouth when you press the trigger…
PRACTICE, PRACTICE, PRACTICE!
As stated, metallics can be very challenging. This is because their pigments are just plane weird—and I know something about both paints and weirdness, as others can testify… Bottom line is that metallic paint ages much faster than other colors. It can look fine in the bottle, when it's reduced for spraying, but then look awful sprayed on the surface. There is no way to ressurect metallic paint that has gone off. The other thing about metallics is that the pigments are often very sensitive to incompatible solvents. The solvent you use can be compatible with the binder, but play havoc with the metal pigment, and you won't know until it dries and cures. Mineral spirits is generally compatible with metallic enamels (there are exceptions, but they are rare). It also evaporates more slowly than other solvents, and this is very necessary with metallic paints.
Also, with metallics, it is often best to build up multiple thin coats, at least initially.
PRACTICE, PRACTICE, PRACTICE!
And did I mention: PRACTICE! That's where consistent results come from.