In this work, the structures, phase sequence, and metallic properties of K₂S have been systematically explored. We confirm that the P6₃/mmc phase is the best possible candidate for the stable structure of K₂S at low pressure range. Although the phases of P6₃/mmc and Cmcm K₂S are semiconductors, two new structures of P6/mmm and Pm1 emerge with metallic characters at high pressures. The analyses of electronic localization functions reveal that the conductivity mainly comes from the electrons surrounding S atom chains, which supplies a potential way to improve the conductivity of sulfur to enhance the electrode recharge ability and rate capability in alkali sulfide battery under pressure.