  We study the Mott transition in Hubbard models with a degenerate band on
different 3-dimensional lattices. While for a non-degenerate band only the
half-filled system may exhibit a Mott transition, with degeneracy there can be
a transition for any integer filling. We analyze the filling dependence of the
Mott transition and find that $U_c$ (the Hubbard interaction $U$ at which the
transition takes place) decreases away from half-filling. In addition we can
change the lattice structure of the model. This allows us to study the
influence of frustration on the Mott transition. We find that frustration
increases $U_c$, compared to bipartite systems. The results were obtained from
fixed-node diffusion Monte Carlo calculations using trial functions which allow
us to systematically vary the magnetic character of the system. To gain a
qualitative understanding of the results, we have developed simple hopping
arguments that help to rationalize the doping dependence and the influence of
frustration on the Mott transition. Choosing the model parameters to describe
the doped Fullerides, we can make contact with experiment and understand why
some of the Fullerides are metals, while others, which according to density
functional theory should also be metallic, actually are insulators.
