Metal has so many subgenres and classifications it can be impossible to keep up with them all. It's so complicated at times that some bands don't even know what kind of music they play, and some self-described fans of certain subgenres have no idea what they're talking about. Not to mention all the bands who play versions of a certain subgenre but aren't considered "true" bands of that genre; looking at Deafheaven and black metal here.
With that in mind, it's a fool's errand to try to define any subset of metal with any sort of certainty. What do you do with all the bands that incorporate some parts of the genre and not all of them? What do you do with the bandwagoners and trendy bands who just want to get in on what's popular right now? What about crossover bands?
That being said, I'm going to try to elucidate here what's really going on right now. The biggest trend in metal these days is djent, a new-ish form of technical, progressive metal that's really captivating audiences and musicians alike. But what the hell is it anyway?