Metal is metal and you can paint any metal
Yes, it is just that simple... just be sure the surface is thoroughly scuffed before you paint. Paint does not molecularly bond to metal it adheres and those minute scratches is what makes the difference in how well it adheres.
You can paint a sheet of glass and it will stick and as long as you don't expose it to weather or abrasion... like painted signs on store windows. But trucks are exposed to all of the conditions that would deteriorate that bond.
