After Effects cannot generate a virtual 3D model of your green sculpture. The way I would approach the project would be to rotoscope the object's faces then use the roto layers as track mattes for layers with gradients applied to simulate lighting effects. You may be able to use Camera Tracking to add 3D layers to the scene and then use the roto to blend those 3D layers with the original. It all depends on your shot. Here's one approach using your shot as a reference:
I have rearranged the panels so you can see the modified properties. This assumes that I have camera tracked the scene and added a reference solid that lines up with the face of the sculpture. The Face 3D layer has been masked with a rotoscoped layer to match the curves of the sculpture. A light as been added to the scene in the approximate position of the actual light source. The Face 3D layer is just a solid that is 50% gray. The color is important because of the blend mode. To simulate the lighting changes as the camera moves around the scene the material options for the layer have been modified as shown. The blend mode is set to Overlay which will lighten anything brighter than 50% and darken anything darker than 50% in the underlying layer so the real shadows in the scene will give the overlay a more natural look.
If you wanted to add a metal texture you could use some stock images of metal surfaces like this:
This assumes you can get a good camera track and that you know or learn how to work in AE's 3D space and do rotoscoping. The project will take some hand work and some experimentation. If you cannot get a good Camera Track of the scene you may have to do everything by hand or use different techniques to generate the highlights.