Metal surfaces can be painted with various types of paints depending on the type of metal, but if it is an aluminum surface, then a water-based acrylic paint should be used. Copper and bronze surfaces use oil or acrylic paints.
Aluminum surfaces tend to have to be scrubbed with an abrasive pad before they are coated. Methylated spirits must be applied to brass in order to do the same thing. Copper is similar to brass in that it may have to be cleaned first. Once this is done, the copper should be coated with a red oxide metal primer.
Some people may need to paint a ColorBond surface, which is simply galvanized or zincalume steel that comes prepainted, but if the paint wears off it can be touched up with a ColorBond spray pack. If the ColorBond has been worn down by weather, it should be washed down to remove the chalkiness before applying a fresh coating.
People must be careful when applying a fresh primer to galvanized iron because the surface layer of zinc will attack oil-based paints, so water-based acrylic paint should be used. This tends to be the same case for gutters and zincalume surfaces because they have the same chemical characteristics.
If someone is trying to paint rusty steel, they must first remove all the rust and then apply an oil-based primer. In this case, the thicker the primer, the better, so stay away from watered-down primers. At a bare minimum, a metal primer should be put on followed by two coatings of an oil-based paint.