Two dimensional (2D) transition metal dichalcogenides (TMDs) are being studied for devices that utilize electrochemistry. Examples include hydrogen evolution reaction catalysis and energy storage. Typical semiconducting 2D TMDs are not well suited for catalysis or energy storage because they are not sufficiently electrically conducting. To circumvent this issue, metallic edges of TMDs have been used to increase the catalytic performance. Increasing strain in 2D materials generally leads to an increase in the density of states at the Fermi level and therefore the electrical conductivity. In addition to increasing the fraction of edges and strain, it is also possible to introduce semiconduction to metallic phase transformation in 2D TMDs by chemistry. The metallic TMDs exhibit exceptional electrochemical properties as catalysts for evolving hydrogen and storing charge in supercapacitors. In this talk, I will highlight the fundamental structural properties of 2D TMDs and correlate them to mechanisms responsible for the electrochemical behavior of 2D TMDs.