  We analyze perturbative aspects of gauged matrix models, including those
where classically the gauge symmetry is partially broken. Ghost fields play a
crucial role in the Feynman rules for these vacua. We use this formalism to
elucidate the fact that non-perturbative aspects of N=1 gauge theories can be
computed systematically using perturbative techniques of matrix models, even if
we do not possess an exact solution for the matrix model. As examples we show
how the Seiberg-Witten solution for N=2 gauge theory, the Montonen-Olive
modular invariance for N=1*, and the superpotential for the Leigh-Strassler
deformation of N=4 can be systematically computed in perturbation theory of the
matrix model/gauge theory (even though in some of these cases the exact answer
can also be obtained by summing up planar diagrams of matrix models).
