  The steady advance in core-collapse supernova simulations requires a more
precise description of neutrino processes in hot and dense matter. In this
work, we study the rates of charged-current (CC) weak processes with
(anti)muons in supernova matter. At the relativistic mean field level, we
derive results for the rates of CC neutrino-nucleon reactions, taking into
account full kinematics, weak magnetism and pseudoscalar terms, and
$q^2$-dependent nucleon form factors in the hadronic current. In addition to
muonic semileptonic processes we also consider purely leptonic processes. In
particular, we show that inverse muon decay can dominate the opacities for low
energy $\nu_\mu$ and $\bar\nu_e$ at densities $\gtrsim 10^{13}~\rm{g~
cm^{-3}}$.
