  In this paper, we generalize the idea in our previous work for the
Vlasov-Amp\`{e}re (VA) system \cite{cheng_va} and develop energy-conserving
discontinuous Galerkin (DG) methods for the Vlasov-Maxwell (VM) system. The VM
system is a fundamental model in the simulation of collisionless magnetized
plasmas. Compared to \cite{cheng_va}, additional care needs to be taken for
both the temporal and spatial discretizations to achieve similar type of
conservation when the magnetic field is no longer negligible. Our proposed
schemes conserve the total particle number and the total energy at the same
time, and therefore can obtain accurate, yet physically relevant solutions. The
main components of our methods include second order and above, explicit or
implicit energy-conserving temporal discretizations, and DG methods for Vlasov
and Maxwell's equations with carefully chosen numerical fluxes. Benchmark
numerical tests such as the streaming Weibel instability are provided to
validate the accuracy and conservation of the schemes.
