Intro to Materials in Unreal
This video will walk you through the steps to make a simple brass material procedurally in the Unreal Engine.
Some of the best sites to download PBR Material texture maps:
https://polyhaven.com/
https://ambientcg.com/
https://www.cgbookcase.com/textures/
https://freepbr.com/
https://www.sharetextures.com/assets