Bullion is a metal thread made from very fine wires wound into a tubular shape. It is very similar to purl metal thread. The main forms of bullion are: a) Bright check bullion, which has a faceted (zig-zag) and very shiny surface; b) Wire bullion, which has a smooth surface and is matt in appearance; c) Bright bullion, which is a form of bullion that has a smooth surface and is shiny in appearance.