  The existence and construction of exponentially localised Wannier functions
for insulators is a well-studied problem. In comparison, the case of metallic
systems has been much less explored, even though localised Wannier functions
constitute an important and widely used tool for the numerical band
interpolation of metallic condensed matter systems. In this paper we prove
that, under generic conditions, $N$ energy bands of a metal can be exactly
represented by $N+1$ Wannier functions decaying faster than any polynomial. We
also show that, in general, the lack of a spectral gap does not allow for
exponential decay.
