The fluorinated graphene has become a rising star of graphene-based systems due to its high stability and interesting properties, e.g., a high room-temperature resistance, optical transparency, tunable band gaps, and magnetic properties. The geometric, electronic, and magnetic properties are investigated for all the halogen-adsorbed graphenes. The essential properties of halogen-doped graphenes are investigated for the distinct adatoms, concentrations, and distributions. The electronic and magnetic properties are dramatically altered by graphene halogenations, such as the Dirac-cone structure, the Fermi level, the free carrier density, the energy gap, the adatom-dominated bands, and the spin configurations. The halogenated graphenes might present the ferromagnetic spin configuration under the same adsorption sublattice, as observed in hydrogenated systems. There are certain important differences between halogenated and hydrogenated graphenes in the spin-dependent properties, namely the metallic or semiconducting behaviors, the uniform or nonuniform magnetic-moment contributions from each non-passivated carbon atom in a unit cell, and the spin density concentrated near adatoms or carbons.