Well that really depends on what you are after Gourry. Like I don't think I can do justice to all the things that happened over the years. I can give you a cliffs notes though on stuff I know about and what has really hit me.
The short of it though is that what happened was even more and.more branched sub genres. A lot of them were technically around in early 2000s but they were fringe things. You were clearly around when we were back and forthing on the symphonic and prog metal scene of Nightwish and dream Theater etc. That stuff never really went away (Within Temptation noted above is the jumping back on point), but we have had a more revival and return to what people joke about being "Cookie Monster vocals" as there has been a movement of *core genres (substitute * with Death/Metal/Math etc). Those tend to focus a lot on your heavier bass and guitar lines, along with that has pretty traditionally come the aggressive growl vocal delivery, so we are seeing that again but at least these days you are seeing a lot more range to it instead of just one tone/octave. They also tend to have an emphasis on technical playing or at least cool riffs , so you will see a lot of pretty fast playing that if not well done at least tends to sucker in the people that think of Thrash as technically impressive. The last few years we have also seen a push towards some production effects in the music as well (for more than just fixing up shitty playing and regular mixing).
For the example of where that finally is for example from this Aversions Crown album
The Glass Sentient is a good example. The opening sequence is muted for effect in the mix (not a great example of production in songs, but there it is). The song has a killer beat and those opening drums are super aggressive, the lead guitar is fast playing, but to hit that perfectly live is pretty killer. The vocalist is the same one the whole song, but you can see three distinct variations on the growl, his lows and middle tone is pretty standard and the higher pitch "pig squeal" has become more prevalent in the last decade or so.
There is movement in other spaces as well though. The symphonic stuff hasn't gone anywhere, Europe still has an industry full of black metal bands and stuff. There has even been a resurgence of Thrash. One of he bigger movement that is getting traction is proper old Hard Rock/heavy Metal bands. You will see them come up a bit in mc's music topic since she seems to have an affinity for metal that sounds like Iron Maiden and that ilk. Hell even outside the edges of Metal I found a rock band that I love because their sound is straight up Black Sabbath.
When I am not posting from an iPad I can dig up points of reference for these,but the short of it with naming names to look up I would say the evolution goes something along these lines (noting that these are just guys I like and are probably just popular, not necessarily pioneers).
Early 2000s we had In Flames, then the kind of stuff Dillinger Escape Plan do picked up. What they do is essentially destroy everyone's brain in a 2km radius so things like Parkway Drive because popular because regular people can actually listen to their stuff and understand "time signature" and "rhythm" and "not having band members bleed on them during shows" (so you know, lame people who hate fun). That takes you through 2000-2010 really, then there is stuff like Suicide Silence building up a scene where stuff gets a bit heavier. Then you have stuff like Bring Me the Horizon crossing over as well and there is a real scene with that production influencing your album a lot and that gets you to this year really.
That is just the stuff I know, there is huge gaps. I was out of following metal for a while this last decade or so as well. Making friends with people in the scene has bout me back into it.
Oh the highlight for craziness though is if you liked or knew Sepultura back in the day, listen to their new single blind without checking out there other stuff. It is amazing how it is clearly Sepultura but is also nothing remotely close to their old stuff in tone.
Sarah Blasko - Planet New Year.
