We all (should) know about the traditional metal ideology dating to the early '80s or so which includes the view that bands that have too much melody in their music and/or go for the money are pose(u)rs. That includes glam, metalcore, nu metal, and alt metal (and in some people's views power metal, gothic, etc.). The only true metal is traditional metal, thrash metal, and underground bands.

I personally started listening to metal about two years ago, as a freshman in high school. I still remember hearing songs like "Your Betrayal" by BFMV, "Last Man Standing" by HammerFall, "Engel" by Rammstein, "Dragula" by Rob Zombie, "Monster" by Skillet, and "Enter Sandman" by (uh, who made that song again ) that got me interested in heavier music. I knew I liked what I was hearing (although I thought the video for "Engel" was kinda weird and gothic), but I couldn't tell the difference between metal and straight hard rock, so I put "heavy metal (music)" into Wikipedia and started looking into the difference. From there, I found bands like Black Sabbath, Metallica, and Iron Maiden (having already heard some songs by the former two before, without realizing it), and got into those bands. While on YouTube I found one of those retarded "true metal vs. false metal" videos that had classic, thrash, death, and black metal as the "real metal" and nu metal, metalcore, and alt rock as the "poser metal." This was reinforced by an entry for metal that I found on Urbandictionary that said at the bottom, "Nu-metal and metalcore ain't metal."

So basically I was left as a newborn metal fan (who didn't really identify myself as a metalhead until at least a year later, having gotten to know a ton of different styles and grown a liking for many of them in the process) who only knew that high screaming = metalcore/screamo = poser metal (at least before I learned how to identify "trve" black metal) and wankster/goth/emo look = poser fags. I later came to understand that mainstream bands were sellout fags (including my Metallica, whose old stuff I'd grown enough liking for not to give a fuck that they sold out in 1991) because they were in it for the money, and that a common method of selling out was to soften down your music to get a wider audience.

With this mentality, I got into actually listening to these new types of metal: black, thrash, death, metalcore, hard rock, etc. To be able to tell the difference between them. I got into the more underground and old-school stuff because those were the true styles of metal. And if a band suddenly released an album with a softer sound, then they must be sellout fags. Seriously, I remember a quote that I made several months ago on the YouTube video for one of the new Ahab songs from their album The Giant, which was a lot more melodic doom/post-doom than their funeral doom debut The Call of the Wretched Sea, saying that they had sold out. Looking back on it now, I realize that they still play a style that is far from ever being mainstream, and had changed because of the development of their own style, which is as "metal" as hell. So I listened to my true metal, over time adding deathcore to the list of styles to hate and power metal, doom metal, stoner metal, sludge metal, grind, and prog to the styles to appreciate.

To this day I prefer the older and more underground styles to mainstream metal as a rule of thumb, for the simple reason that I've grown accustomed to those styles and been trained as to what "poser shit" to look out for. However I've come to the realization that many of the more mainstream bands, if overrated, sound as much like "real metal" as a lot of the off-the-beaten-path stuff I listen to (like doom metal and the occasional experimental band) and consider metal which other metalheads might not think is real metal. (And likewise a lot of "true" old-school bands are probably overrated quality-wise, despite having been highly influential.) I make a point of sampling some songs by different "poser" bands to see if they sound like metal, having come to conclusions about which ones are "true." And I've decided that some bands from all those styles I brought up are metal, some are not. And most of the ones that aren't don't really give a fuck, and I respect that. They're not really poser metal if they don't claim to be metal, eh?

As for whether bands like Metallica have changed their style for the money, and therefore are sellouts, is not my place to judge, since I've never been in the situation of being pressured by a label to play a certain style, knowing that it'll put my band in the "big, big leagues," as their producer at the time of the Black Album put it. Our gods Judas Priest had a time when they played a more mainstream style that had somewhat of a glam sound to it. (That was just an alternative example, since bands in virtually every style have at some point played something that intentionally or unintentionally sounded like a more mainstream style, and either went back to their old style or ran with their take on the mainstream one.)

And to this day, I occasionally ponder on whether certain bands or songs I like are "real metal," because it's been so ingrained in my head that whether it's metal vs. hard rock determines its quality. But then I realize how juvenile that is, and how much that mentality resembles that of the metal elitists who had my view of metal fucked up for so long. And I just let the song blare.

TL;DR: Vote on the poll and post about how the elitist viewpoint of some metalheads has affected your opinions/tastes. I would vote on the first option.