The continued increase in the use of metals over the twentieth century has led to a substantial shift from geological resource base to metal stocks in society. Such a shift raises social, economic, and environmental issues that require quantifying the amount of stock of 'metal capital' utilized by society. This report reviews the relevant literature on this topic. From a compilation of 54 studies, it is clear that a reasonably detailed picture of in-use stocks and in-use lifetimes exists for only five metals: aluminium, copper, iron, lead, and zinc, and in only two cases have spatial stock allocations been performed. Limited data suggest that per capita in-use stocks in more-developed countries typically exceed those in less-developed countries by factors of five to ten. Sparse but potentially useful in-use stock information exists for nineteen other metals. There is a little information on stocks in government repositories, and essentially none on stocks in 'hibernation', in tailings repositories, in industrial stock- piles, or in landfills, nor on typical in-use life-times for almost the entire periodic table of the elements. Outflows from in-use stocks, potentially useful for determining future rates of reuse, can currently be reliably estimated only for aluminium, copper, iron, and lead. This is the first of six reports on the stocks and flows of metals, the last of which will draw upon the first five to address criticality and policy options related to the sustainability of metals.