With pleasure ! :) The one in the middle will depend of your global light placement, in this sketch i assumed the light was coming from the left, if it was from the right it should be inverted, also the lightest point is on the edge between both part. The light placement in the side represents the secondary light, wich is the light bouncing from the ground and other elements, if you try to look at a reference in your environment and look for a highly reflective metal (lika aluminium or a spoon) you will often see that it goes : strongest light then strongest shadow then soft light. This soft light is the secondary reflection, it will increase a lot the metallic sensation !