Primer for Metal Figures

Mr surfacer 12 spraycan

I have used Model Master primer succesfully on numerous figures, and have also used the Citadel primer and Gunze Sangyo primer. The Gunze was very good, but is pretty hard to find in the US. I think it's called Mr. Primer, but I don't have a can on hand to confirm. The Model Master and Citadel are both readily available, I use whichever is cheaper when I'm shopping (usually the Model Master).
The most important part of painting metal figures is making sure that the casting is clean before you apply anything, including primer. I soak all my figures in dish detergent for anywhere from a couple of hours to overnight. Then I scrub them with a soft toothbrush until the surface is clean, holding them under clear running water several times during the process and at the end. Paint, primer and glue can't hold onto the figure unless it's very clean.

I don't know about using automotive primer for metal figurines, cars are made out of one sort of metal and the figurines out of something totally different.

If you live near a shop that retails supplies for the various "Games Workshop" games and the pewter figurines you can buy for them, you might want to pay them a visit. The best primer I am aware of for metal figurines is made by a company called Citadel Miniatures, Its specially formulated for use on metal figurines. It can be brushed on by hand or thinned for airbrush use. Its also available in a spray can. It goes down very nicely and doesn't obscure detail at all.

It is water based acrylic, but as with all acrylics, once its cured properly you can put any other sort of paint you want over it.

If you're in America, this stuff should be very easy to find.

Hope that helps you