Performed density-functional theory (DFT) calculations have shown that the Li adsorption on the MoS2 (0001) surface, as well as Li intercalation into the space between MoS2 layers, transforms the semiconductor band structure of MoS2 into metallic. For the (root 3 x root 3) - R30 degrees Li layer, the band structures of the MoS2 bilayer with adsorbed and intercalated Li are very similar, while for higher Li concentrations, the character of metallization for the adsorbed layer substantially differs from that of the MoS2-Li-MoS2 layered system. In particular, for the adsorbed (1 x 1) Li monolayer, the increased density of the layer leads to the nonmetal-to-metal transition, which is evident from the appearance of the band crossing EF with an upward dispersion, pertinent to simple metals. It has been demonstrated that intercalated Li substantially increases the interlayer interaction in MoS2. Specifically, the estimated 0.12 eV energy of the interlayer interaction in the MoS2 bilayer increases to 0.60 eV. This result is also consistent with results of earlier DFT calculations and available experimental results for alkali-intercalated graphene layers, which have demonstrated a substantial increase in the stiffness due to intercalation of alkalis. (C) 2015 Elsevier B.V. All rights reserved.