Understanding how metal species behave, and what adsorption structures they form on transition metal dichalcogenides is important for targered material design for many technologies including catalysis, sensors and next generation transistors. We have presented an extensive first principles DFT study on the interaction of Cu n clusters, with n = 1 -4, on monolayers of the TMDs WS 2 , WSe 2 , and WTe 2 , which show great promise for many applications. The interaction of Cu with these monolayers at the sub-nanometre scale is required in order to understand the fundamental interactions between Cu and WX 2 monolayers, and their role in nucleation of metal films. By investigating these interactions on three different TMD substrates, the role of the chalcogen in these interactions can also be understood. Furthermore, comparing these results to previous work on MoS 2 can reveal the role of the metal species of the TMD.