(M)ost metals form an oxide layer when exposed to oxygen. Some are bad, but some "passivate" the surface, protecting it from corrosion (e.g., aluminum)
(M)any materials experience "fatigue", where, because of cyclic loading, they'll begin to deform or even fail well below their theoretical yield strength
Small particles in a gas or liquid constantly (m)ove around randomly. Work on this "Brownian motion" led to the acceptance of atoms as physical reality
