Wetness and why materials change shape

[kosovo dave]

Why is is that certain materials -- like plastic, metal (assuming it doesn't rust), glass -- retain their shape when they get wet, and some materials -- like paper -- don't return to their original shape even after they become dry again?

My knowledge of chemistry is pretty limited, but my initial guess would be that it has something to do with polarity or new bonds forming/old bonds breaking.

 

[wazani]

Hi...

For metals and some kinds of plastic does not have a strong attraction with water molecules,
so it is not affected when they become wet.
While materials containing hydroxyl groups like paper attached to water molecules by hydrogen bonding and swell .