Metal hydrides have long been used for electrochemical and gaseous hydrogen storage. They will play an important role in the future Hydrogen Economy if much-needed materials R&D on them are ultimately successful. This paper will provide broad thermodynamic and phenomenological introductions to rechargeable metal hydrides in order to set the stage for subsequent speakers on this topic. It will trace their long history from elements through alloys and intermetallic compounds to modern complex hydrides. Problems and challenges for their potential use as vehicular H-storage will be discussed. Sources of useful hydride data will be outlined, for example the author's on-line Hydride Information Center sponsored by the IEA, US DOE and Sandia National Labs (http://hydpark.ca.sandia.gov). Hydride applications other than H-storage will be briefly summarized.