Historically the term ‘metal’ has beon applied exclusively to solids formed from one of the metallic elements or from alloys containing these elements. However, recently synthesized organic compounds such as TTF-TCNQ have been found to exhibit metallic properties over a wide tomperature range and yet are composed solely of non-metallic atoms such as carbon, nitrogen, sulphur and hydrogen. The organic molecules which form these compounds are large and flat and lie in stacks, with π-molecular orbitals interacting strongly up the stacks and only weakly between them. Thus in addition to being metallic, these compounds are ‘quasi-one-dimensional’ and act as an experimental benchmark against which to test theories of electrons in one dimension. This paper describes the distinctive properties of the class of quasi-one-dimensional organic metals, typified by TTF-TCNQ, and relates them to traditional one-dimensional electron theories and to more recent theories which have been stimulated by work on these unusual materials.