This page gives an overview of the V-Ray Metalness Render Element.
The Metalness Render Element shows areas, where a V-Ray Material, with Metalness is applied. The Metalness values are baked into an image, where black corresponds to 0 and white - to 1. The image created can be used as a metalness mask when creating PBR shaders in post-processing.
Note that values between 0 and 1 give an unrealistic metalness effect. They can be used creatively and for smooth transitions from a metal to a non-metal material on the same geometry. For more information on metalness and it's role when creating PRB shaders, visit Understanding Metalness.
This render element is enabled through the Render Elements tab of the Render Setup window in 3ds Max and displays its parameters in a rollout at the bottom of the window:
VRayVFB – When enabled, the render element appears in the V-Ray Frame Buffer.
Deep output – Specifies whether to include this render element in deep images.