  We review experimental and theoretical work on cold, trapped metastable noble
gases. We em- phasize the aspects which distinguish work with these atoms from
the large body of work on cold, trapped atoms in general. These aspects include
detection techniques and collision processes unique to metastable atoms. We
describe several experiments exploiting these unique features in fields
including atom optics and statistical physics. We also discuss precision
measurements on these atoms including fine structure splittings, isotope
shifts, and atomic lifetimes.
