Substrate is Unreal Engine 5's approach to authoring materials, which replaces the fixed suite of shading models and blend modes, such as Default Lit and Clear Coat, with a more expressive and modular framework.
Getting Started
Substrate Materials Overview
An overview of the Substrate Materials framework for principled BSDF-based material authoring.
Programmer Guides
Programming with Substrate GBuffer Formats
An overview for programmers using Substrates GBuffer formats in their shader code.