I've been thinking about this question for a while now, and I just had to post it.
I've been around kids and young adults who wear shirts depicting bands such as Asking Alexandria, Bring Me The Horizon, Avenged Sevenfold, Black Veil Brides, Suicide Silence, etc. I get curious, and ask them "Hey, what does that logo on your shirt mean?", and they would respond that "It's a metal band." I would go and listen to some songs from these bands and, believe me, they sound pretty decent. I got into some songs from these bands, and listened more songs from these bands, and got into the bands themselves. I tell people that my bands are metal, and they look at me with disbelief, saying that the bands I listen to are "not metal", and are "poser" bands pretending to be metal. I was slightly offended with their statements, and did some research about them, and the same thing: "not metal" and "poser" trying to be metal when they are actually not. Ridiculous! I am no longer into that stuff, I am into the "true" metal (Death Metal, Melodic Death Metal, Symphonic Black Metal, etc.), but I still occasionally listen to the Metalcore and Deathcore bands I used to listen to. Is there a "true" metal bands nowadays?
People say that anything "-core" isn't metal, but they often forget that half of the "-core" bands out there are more METAL than "-CORE". Metalcore is, as we all know, a fusion genre of Heavy Metal (the more "extreme" type) and Hardcore Punk. Thrash Metal derived from Hardcore Punk, and Death and Black Metal derived from Thrash Metal. Blast beats derived from punk, as well. Today's "true" Metal came from punk rock and Hardcore punk. Metalcore and Deathcore are subgenres of metal, they are fusion genres of Metal and Hardcore Punk.
What if the bands people say who "aren't metal" weren't trying to be metal in the first place? What if the fans of those bands never thought they were metal in the first place? (i.e. Avenged Sevenfold, although I don't know if whether or not they ever intended to be metal at all).
The bands on those kids and young adults' shirts ARE metal. This thread you just read was written by a metalhead, who is myself.