How to explain bonding in terms of physics? Give examples.

Bonding from the point of view of physics is quite simple to explain. Bonding is the diffusion or interpenetration of particles of one substance into another. For example, if you put a lead ingot on a gold ingot, then in five years we will be able to see a thin layer, which arose as a result of diffusion. It should be borne in mind that both plates must be perfectly polished and tightly pressed against each other.