  Knowledge of the metallicities of M dwarfs rests predominantly on the
photometric calibration of Bonfils and collaborators, which predicts that M
dwarfs in the solar neighborhood, including those with known planets, are
systematically metal-poor compared to their higher-mass counterparts. We test
this prediction using a volume-limited sample of low-mass stars, together with
a subset of M dwarfs with high-metallicity, F, G amd K wide binary companions.
We find that the Bonfils et al. photometric calibration systematically
underestimates the metallicities of our high-metallicity M dwarfs by an average
of 0.32 dex. We derive a new photometric metallicity calibration and show that
M dwarfs with planets appear to be systematically metal-rich, a result that is
consistent with the metallicity distribution of FGK dwarfs with planets.
