This guide should is designed to export your PBR Metallic/Roughness textures from 3dsmax to blender.
We will take our PBR textures, place them into a standard material and export to FBX. FBX settings are based on your preference and dont affect the material. Just be sure to check your units scale factor if you work in units other than meters.
Specular Level: 0.25 = Specular 0.5 in Blender
Reflection = Checked On, but 0% which turns off Metallic on import
Normal Map: DirectX texture in 3dsmax, I swap this to OpenGL texture for export to blender.
Roughness texture in Glossiness slot.
Same as above except swap the Reflection channel to 100% for Metallic objects (or place the Metallic map here)
If you want to control the Specular yourself using a 0/1 Map then place this into Specular Color (3dsmax). This will transfer this to the Specular Channel (blender).