  The rotation rates and magnetic activity of Sun-like and low-mass (< 1.4
Msun) main-sequence stars are known to decline with time, and there now exist
several models for the evolution of rotation and activity. However, the role
that chemical composition plays during stellar spin-down has not yet been
explored. In this work, we use a structural evolution code to compute the
rotational evolution of stars with three different masses (0.7, 1.0, and
1.3Msun and six different metallicities, ranging from [Fe/H]=-1.0 to
[Fe/H]=+0.5. We also implement three different wind-braking formulations from
the literature (two modern and one classical) and compare their predictions for
rotational evolution. The effect that metallicity has on stellar structural
properties, and in particular the convective turnover timescale, leads the two
modern wind-braking formulations to predict a strong dependence of the torque
on metallicity. Consequently, they predict that metal rich stars spin-down more
effectively at late ages (> 1 Gyr) than metal poor stars, and the effect is
large enough to be detectable with current observing facilities. For example,
the formulations predict that a Sun-like (solar-mass and solar-aged) star with
[Fe/H]=-0.3 will have a rotation period of less than 20 days. Even though old,
metal poor stars are predicted to rotate more rapidly at a given age, they have
larger Rossby numbers and are thus expected to have lower magnetic activity
levels. Finally, the different wind-braking formulations predict quantitative
differences in the metallicity-dependence of stellar rotation, which may be
used to test them.
