glTF 2.0 specification only supports exporting PBR materials based on a metallic-roughness model.

Material support for Blender's glTF exporter only works for Cycles render materials at the moment.

And even then it requires a specific node setup to be used, as mentioned in the [user documentation][1], through the use of a Node Group designed for this purpose. The node group is [available for download][2] from the repository.

For future versions, EEVEE material node tree support is planned, using the Principled BSDF Shader, but it is unavailable at the moment.

Also see