Procedural Metal Materials Bundle 

Materials: 77 (based on 19 different Group Nodes)
Render Engine: Mostly Cycles, there are some eevee compatible materials too, you can check the documentation for each material compatibility.
Material Artist: Sanctus
Materials Documentation: https://sanctuslibrary.xyz/documentation/main/en/topic/metals
Using Mapping: How to use Mapping node with this materials

The bundle is an Asset Browser compatible file with all the 77 materials with custom thumbnails in it:

You can also Bake procedural materials using the free version of my addon Sanctus Library ▼

This materials are also sold as part of the Sanctus Library addon
along with hundreds of other materials.