Procedural rainbow metal material. Without textures (maps such as Noise Smoke are used) does not require UV or any mapping. Easily edited in the mat editor you can change the color size of patterns and other parameters.
-The size of the blank in the preview is about 30cm
-There are two additional materials in the scene:
Material 1 iridescent changes color depending on the angle at which the material is rendered (short demonstration on animation video here https://www.youtube.com/watch?vYns9lVrTeh8)
Material 2 has just a vertical gradient