Dark Metro is your standard horror manga. It's episodic so far and uses basic set ups. At the beginning it's fun and fairly well executed. I wouldn't call it the best in its genre but it's far from the worst. Especially considering that it's collections of short stories and not a long and involved plot.
Unfortunately it goes down hill from there when it gets to volume two. The stories become a bit shorter and have less plot to them. Plot ideas that could be interesting if there was more buildup and detail fall flat when shrunk to only a few pages. The main repeating character
starts out in the first volume as mysterious but not entirely unreal. By the time you get to the end of the second volume however he seems like a badly fleshed out mary sue. None of his powers are explained or even witnessed outside of him showing up at the end of each chapter to defeat the bad guy and make it so nothing actually happened in the chapter.
Overall this series is a collection of decent ideas that haven't been worked with at all, combined with a bunch of really generic ideas that haven't been fleshed out either.