As I sit and listen to the new Avenged Sevenfold record, I can’t help but think of the history of metal music and how much disagreement there is over it. It’s hard to find two people who agree on what makes a band truly metal or when the genre began.

One faction of people believe that Led Zeppelin was the first true metal group. This is a ridiculous notion, as Zeppelin was much more of a blues-rock band than anything. The album “Led Zeppelin III,” despite opening with the classic headbanger “Immigrant Song,” featured a number of songs that were clearly folk-influenced.

Perhaps a few of Zeppelin’s songs did accurately fit the description of early metal, but the group’s sound didn’t consistently have enough of those elements to warrant calling it metal as an entire band. “Helter Skelter” by the Beatles was much more metal than anything Zeppelin did, and nobody considers the Beatles to be a metal act. So while Zeppelin influenced many of the first metal bands, it doesn’t make it a part of the genre. By that logic, we’d have to keep going back through the years of who influenced whom, and eventually we’d determine that Beethoven is metal. I don’t think so.

Another group gives Black Sabbath the credit for starting heavy metal music, which is much more accurate. When you compare Sabbath and Zeppelin, the instrumentals are actually fairly similar: Zeppelin’s “Whole Lotta Love” has the same driving eighth-note feel of Sabbath’s “Paranoid,” and “Black Dog” employs a call-and-response structure similar to that of “War Pigs.” The big difference between the two comes in the lyrics, which is where Sabbath proves to be way more metal than Zeppelin.

While Zeppelin’s Robert Plant was singing about love, Lord of the Rings and his genitalia, Sabbath’s Ozzy Osbourne was tackling war, death, witchcraft and insanity. Both of them had similar vocal styles —you can almost imagine them singing each other’s songs — but the subject matter is worlds apart.

With how far music has come in the years since these bands, it’s hard to look back and consider anything from those days as heavy. Today we have sub-genres such as black metal, thrash metal, death metal and sludge metal that make Black Sabbath look like The Monkees.

However, if you listen back to those early metal albums, you’ll find that the songwriting remains truly heavy to this day. People often forget that technology in the ’60s and ’70s couldn’t create the thick guitar, bass and drum sounds that we take for granted. If you can get through the generation gaps in production and think about what the musicians are actually doing, you’ll find that most of them would have no problem standing up to our contemporary heavy music.

Today, metal music has found its way into nearly every other existing genre. Rap-metal pioneers Rage Against the Machine remain as popular as ever, and bands like Dream Theater and Meshuggah have expanded on the prog-metal tradition started by King Crimson and Rush, mixing heavy riffs with elements of jazz. Even the female pop artist Orianthi has a legitimately metal guitar solo in her hit “According To You.”

Genre-blending is almost always a positive thing because it demonstrates growth in the music world, but it comes with its downsides. In the case of metal, this cross-pollination can frustrate and even anger metalheads, as though 15-year-old Orianthi fans are taking metal away from the masses and giving it a bad name. They would say it dilutes the genre, weakening metal music as a whole. I don’t buy that — I still enjoy Metallica just as much as if Orianthi didn’t exist, but maybe I’m just not hardcore enough.

As metal continues to be incorporated into just about every kind of music that’s out there, disagreements on what constitutes heavy music will only grow. Music will keep getting heavier, and it will be even harder to determine who the founding fathers of this genre were as we distance ourselves from them in time. At least we have visionaries like Metalocalypse’s Nathan Explosion to give us some direction: “Playing acoustic is totally lame and not metal.”