It's fairly easily explained by just thinking of the surface as being covered in tiny springs, or trampolines maybe. Just these are tiny springs made of electro

It's fairly easily explained by just thinking of the surface as being covered in tiny springs, or trampolines maybe. Just these are tiny springs made of electromagnetic forces. Anything sitting still on the surface is compressing the springs exactly enough until they push back enough to resist further compression, and not enough that they push more. This is a stable equilibrium. The normal force from a surface can exceed the force needed to just push back against the weight of an object, if you can compress the springs enough. That's why things can bounce.