To make scratches on reflective metal show up, use raking light and a low shooting angle.

The key is not to light or photograph the surface straight on. Instead:

• Place the camera low, close to the plane of the surface, rather than directly above it.
• Light the metal from the side, so the light skims across the surface.
• An off-camera flash or lamp at roughly a 45° angle can help create tiny shadows and highlights inside the scratches, increasing contrast.

This side-lighting approach is often much better for showing texture and wear on polished metal than frontal lighting, which tends to flatten the surface and emphasize reflections instead of damage.

In short: photograph along the surface, not down onto it, and use directional side lighting to reveal the scratches.