The search for electrode materials for two-dimensional structures, particularly for semiconducting H-MoS2, is a significant problem for contemporary materials science. This stimulates interest in metastable structures, which motivates us to look at non-stoichiometric metastable states known as Berthollides. An unbiased evolutionary search for new two-dimensional structures in Mo-S system showed the presence of Mo5S4, Mo3S4, and MoS metastable structures (located near the decomposition line) in the low-sulfur area of phase diagram. The predicted novel Cm-Mo3S4 phase exhibits metallic properties and dynamic stability confirmed by the calculation of phonon dispersion spectra. Its lattice parameters are similar to the semiconducting H-MoS2 phase which makes it possible to use Cm-Mo3S4 as a conducting contact in nanodevices based on MoS2. A study of proposed H-MoS2/Cm-Mo3S4 lateral heterostructures showed that in the contact region a transition to the conducting states of the H-MoS2 edge atoms is observed, as well as the preservation of Cm-Mo3S4 conducting properties. The main feature of Cm-Mo3S4 is that it can be structurally obtained by a direct transition of H-MoS2 monolayer with sulfur vacancies. As a result, the predicted Cm-Mo3S4 phase is a promising candidate for conducting contacts in nanoelectronic device components.