From Morrison's Mind: Metal Men after Flashpoint
Before Flashpoint happened Metal Men didn't really move lots of units, but since Didio is a big fan of them it was only a matter of time before they appeared in this "new" continuity. So how was it and can we trace any of it back to Morrison? I don't know if it was a push from Didio or it was Johns' idea, but Metal Men got their first appearances in New 52 JL book. And it is not a random appearance, but they get a decent amount of pages for 2 part story with Cyborg during Forever Evil event. So you know, high profile debut all things considered. Technically Tina appears several issues earlier in JL #18, but I'm not a fan of Trinity crossover (and the road to it) so I'd say that issue can, and probably should, be ignored. Anyway, Cyborg was removed from Titans environment and he needed new allies and enemies. For enemies we got Grid and Metal Men helped Cyborg overcome it. This was basically their origin story so there wasn't anything Morrison related, ...