  Nodal-line metals and semimetals, as interesting topological states of
matter, have been mostly studied in nonmagnetic materials. Here, based on
first-principles calculations and symmetry analysis, we predict that fully
spin-polarized Weyl loops can be realized in the half metal state for the
three-dimensional material Li$_3$(FeO$_3$)$_2$. We show that this material has
a ferromagnetic ground state, and it is a half metal with only a single spin
channel present near the Fermi level. The spin-up bands form two separate Weyl
loops close to the Fermi level, which arise from band inversions and are
protected by the glide mirror symmetry. One loop is of type-I, whereas the
other loop is of hybrid type. Corresponding to these two loops in the bulk, on
the (100) surface, there exist two fully spin-polarized drumheads of surface
states within the surface projections of the loops. The effects of the electron
correlation and the spin-orbit coupling, as well as the possible hourglass Weyl
chains in the nonmagnetic state have been discussed. The realization of fully
spin-polarized Weyl-loop fermions in the bulk and drumhead fermions on the
surface for a half metal may generate promising applications in spintronics.
