A couple of years back, Apple purchased the patents from a materials firm by the name of Liquidmetal. The company made metal alloys that combined high strength with the ability to be formed into complex shapes.
According to 9to5mac, we probably won't see Liquidmetal featured prominently in any upcoming products. Chances are, it's being used in batteries, or possibly even the SIM card ejector tool in which Apple has reportedly tested Liquidmetal parts. 9to5mac also spoke to a Liquidmetal investor who claims it will be a few years "before Liquidmetal can be used in a large scale for Apple products". Whatever large scale entails, hopefully it'll be interesting. [9to5mac via Business Insider]