A metal will not shatter like glass, partially because it has a higher heat-flow efficiency, but chiefly because it has a sturdier intermolecular structure. Metal does, nonetheless, warp for the same reason that glass cracks: structural stress caused by a sudden and significant change in the relative temperature of two closely situated areas of the cookware.
The metal of inexpensive metal pots and pans (except for the cast-iron variety) is typically thin-gauged, and that of higher-quality utensils is thick-gauged. The thicker a sheet of metal, the greater its structural strength, and therefore the less likely it is to warp. Since warped cookware conducts heat unevenly, cheap pots are seldom a bargain.