I changed the roughness of the head a little bit
Render with Arnold, I add some directional light and simulate the light in substance painter, and it looks better and was quite close to the Substance Painter render.
These are the robots rendered in Substance Painter(upper) and Arnold(under). I don’t know why they look so different. I will look at how to render better with Arnold.
I used ZBrush to make a displacement map of the robot’s head to make it look smoother.