Geometry is only the shape
A 3D object can be perfectly modeled yet look flat if its surface response and lighting are poor. Materials describe properties such as base color, specular response, roughness-like behavior, reflection and texture contribution.
Lights provide the illumination context that makes those properties visible. The final appearance is the interaction between geometry, material, light, camera and renderer.
Materials are not 2D color correction
A 2D Color Corrector changes the pixels of an already rendered image. A 3D material changes how a surface is shaded before the scene becomes pixels. That distinction matters for highlights, reflections, normals and the way the object responds as the light or camera moves.
If you need physically coherent surface behavior, solve it inside the 3D/material branch rather than trying to fake every change after Renderer3D.
Classic Fusion materials and USD materials
Classic Fusion 3D materials such as Blinn, Phong and CookTorrance belong to the traditional 3D pipeline. USD material tools belong to the U-node scene system. Both describe surface appearance, but they participate in different scene architectures.
Do not assume that a material node can move freely between classic 3D and USD branches. Match the material system to the scene system you are using.
Lighting is part of composition
Point, spot, directional, ambient and dome-style lighting create different spatial cues. Light direction can reveal form, separate foreground from background and support the visual logic of the plate you are compositing into.
For integration work, match the real shot's key direction, softness, contrast and color rather than lighting the CG object in isolation.
Textures, bump and maps
Texture maps can drive surface color or other material properties, while bump/normal-style maps change how the surface reacts to light without changing the underlying geometry in the same way as actual displacement.
Keep scale and UV/texture transforms under control. A good material can still look wrong if the texture scale or orientation does not make sense for the object.
Where materials and lights belong in the Flow
Materials and lights live inside a scene pipeline, not in the final 2D layer stack. A material must be assigned to geometry, a light must illuminate scene objects, and a camera plus renderer must turn that interaction into visible pixels.
This is why a Material or Light node should not be treated like Color Corrector or Glow. It has no useful final appearance by itself; its meaning comes from the geometry, normals, textures, scene scale and renderer that evaluate it.
Keep scene construction, material assignment and lighting grouped before Renderer3D or the corresponding USD render stage. Apply ordinary 2D grading and optical finishing only after the scene has been rendered.
Practical example: lighting a textured 3D title
Start with Text3D or another piece of geometry, assign a material, feed image maps into color/bump/specular inputs as needed, and place the object into the scene through Merge3D.
Add a key light and optional fill or environment light, position Camera3D, and inspect how the material responds as the object or camera moves. Adjust roughness, specular response and bump strength in relation to the actual lighting rather than in isolation.
Renderer3D converts the lit scene into an image. From that point, use regular 2D Merge, color matching, glow, defocus or grain to integrate the rendered title with the plate.