(M)any materials experience "fatigue", where, because of cyclic loading, they'll begin to deform or even fail well below their theoretical yield strength
I am content. I am *con*tent. Are you content with (m)y content? I hope that with any semantic satiation you're feeling is paired with sexual satiation
(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)