Dirac magnetic monopoles are hypothetical elementary particles. By assuming their existence one can explain the quantization of electric charge, the August Kundt experiment, and the conservation of baryon and lepton number. Here I present a new nomenclature where I redefine isospin and hypercharge. By doing so I explain baryon and lepton number conservation as an effect of the electric-magnetic duality and the $U(1)times U(1)$ gauge symmetry of quantum electromagnetodynamics. By using this method I predict the quantum numbers of an octet of magnetic monopoles. Another surprising result is that both leptons and quarks have nonzero magnetic isospin, a new quantum number. Moreover I show that Dirac magnetic monopoles can form low-mass bound states which are analogous to mesons, baryons, atoms, and molecules. I point out that these bound states could be the major component of cold dark matter. The PandaX Collaboration reported an excess of 4.3 events above the background in the PandaX-4T experiment. The best fit for this excess was obtained for a WIMP mass of 6 GeV. Here I show that both the mass and the interaction cross-section are compatible with bound states of Dirac magnetic monopoles.