  The concept of a disordered Fermi-liquid fixed point is introduced and used
to understand various properties of disordered metals within a unifying
framework. Corrections to scaling near this fixed point give what are commonly
called weak-localization effects. Various instabilities of the disordered
Fermi-liquid phase are discussed. These include two distinct types of
superconducting-to-normal-metal quantum phase transitions. First, the quantum
phase transition from a disordered metal to a conventional superconductor in
bulk materials is considered. Second, a quantum phase transition in two
dimensions from metallic-like behavior to a novel type of disorder induced,
spin-triplet, even parity, superconductivity is treated. The paper is concluded
with a discussion of the nature of the ground state of two-dimensional,
disordered electron systems.
