There are countless instances where we need to make something look like metal in scale modeling. In the past we have had to resort to using metallic paints. This can work fine in many situations, but in some the paint is too thick. One of the easiest, and fastest, ways to apply some metallic coloring is using Sharpie markers. They come in a few shades, gold , silver and copper.
1- One of my favorite uses is to apply the silver marker to a vehicle to create patches where paint has peeled. Simply dab the marker on the vehicle, almost like the pattern of spots on a cow. Then follow up with either some rust colored chalk or artists oils burnt umber or raw sienna. You can apply the same technique to locomotive bodies as well as smaller objects like gas pumps.
2- Guy wires that hold up smoke stacks are often black metal or galvanized metal. Simply color them with a black sharpie marker and follow up with silver randomly, or color them silver all together.
3- When creating copper flashing for a roof ridge, color a strip of grey or black paper with the copper colored Sharpie . Then create a green copper patina finish by dry brushing the strip with a mint green acrylic paint.
4- If you are working on a structure with more fanciful details, like a gold leafed finial, use the gold color Sharpie directly on a finial casting.
As you model more with metallic Sharpies at your workbench, more and more uses will presents them selves. Give it a try.