  The conventional theory of metals is in crisis. In the last 15 years, there
has been an unexpected sprouting of metallic states in low dimensional systems
directly contradicting conventional wisdom. For example, bosons are thought to
exist in one of two ground states: condensed in a superconductor or localized
in an insulator. However, several experiments on thin metal alloy films have
observed that a metallic phase disrupts the direct transition between the
superconductor and the insulator. We analyze the experiments on the
insulator-superconductor transition and argue that the intervening metallic
phase is bosonic. All relevant theoretical proposals for the Bose metal are
discussed, particularly the recent idea that the metallic phase is glassy. The
implications for the putative vortex glass state in the copper-oxide
superconductors are examined.
