What’s makes something shiny?

Question

For example why are some surfaces/materials shiny, like some metals, fabrics, plastics etc. but not others.

[Edit: Thanks, two good answers that explain it well]

In: 2

Answer 1

Depends on how smooth the surface is. If it’s rough on a microscopic scale it will look matte to us.

This has to do with light reflections – a smooth surface will reflect all the light into the same direction and a rough surface will scatter it randomly.