If one were to look over the general timeline of metal's history, there are some trends that can be used to label each decade.

The '70s saw the birth of the genre, with the likes of Ozzy, Halford, Bouchard, and Lemmy paving the road towards a form of music that refused to turn away from the dark corners of society.

Then came the '80s, when metal became a dynasty. Movements ranging from melodic to unrelenting sprouted in New York, L.A., San Francisco, Tampa, and East London.

But it all came crashing down in the '90s. Alt rock and grunge took over, and the genre was largely forced back into the shadows. This past decade, the internet has helped metal make a global resurgence, with new forms of metal coming from places previously unheard of. 

So what will this decade be known for when all is said and done? If major events in the past four years have any indication, the 2010s will be known as the decade when metal had its first passing-the-torch moment. For indeed, the old guard -- the founders of this amazing genre -- are slowly passing away. 

This trend started with the death of Ronnie James Dio in 2010 due to stomach cancer. It was a big punch in the face for everyone in the community. Certainly, there had been major musician deaths before, such as Cliff Burton's bus crash or Dimebag Darrell getting shot.

But these were freak incidents. To lose Dio, one of the most virtuosic vocalists metal has ever produced, to something as crippling as cancer, was arguably the first instance where metal fans were confronted with the mortality of their idols. Later came the death of Slayer's Jeff Hanneman, one of thrash metal's greatest songwriters, due to liver failure. Dave Brockie, founder of the gross and hilarious alien band known as GWAR, died last month of causes to be determined. Both bands have vowed to continue on, but Hanneman and Brockie were both essential parts of what made their respective bands great, and they are truly irreplaceable. 

It's not just deaths, either.  Bands are either showing their age physically or just plain hanging it up. Motley Crue will be embarking on their farewell tour this summer. Malcolm Young has become "seriously ill" and has to take an indefinite break from AC/DC. All of Lemmy's years of booze and drugs have caught up with him, leading to Motorhead canceling tour dates this past winter (though to his credit, Lemmy's still capable of giving a strong performance if his recent shows at Coachella and Club Nokia are any indication). 

And then there is the first guitarist of heavy metal, Tony Iommi, who was diagnosed two years ago with lymphoma that he says he will have to deal with for the rest of his life. He's taken time in between tours for treatments to keep the cancer in check, but his condition has left the future of Black Sabbath, metal's founding fathers, in uncertainty. 

For this reason, Black Sabbath's performance on Saturday at the Hollywood Bowl, while not a farewell performance, did have just a slight undercurrent of finality to it. The fact that this show even happened is a bit of a surprise.

The band already did a U.S. tour in support of their Grammy-nominated album '13' last fall; But in between their just-finished tour of Canada and their upcoming tour of Europe that will conclude on July 4 in Hyde Park, a one-off show at the Bowl was thrown in. It's only the second time Sabbath has performed at the historic venue, and the last time they performed there in 1972, Iommi collapsed during the performance. 

This time, though, Sabbath was determined to put on a show that none of the nearly 18,000 in attendance would ever forget, and they definitely succeeded. Despite Iommi's disease, despite Ozzy Osbourne's struggles with substance abuse, despite original drummer Bill Ward dropping out of the band's reunion due to contract disputes, here they were, enjoying one last run at the top of the music world and performing with the kind of power and exuberance that they had as a bunch of 20-something, long-haired Birmingham ruffians.

The setlist was largely a greatest hits compilation. The tried-and-true selections -- "War Pigs," "Iron Man," "Black Sabbath," -- were all there, with '13' getting some representation with "Age of Reason," "God Is Dead?", and "End of the Beginning." Ozzy was mixed on the mic. On some songs, particularly the ones mentioned above, he didn't miss a note. Gone was the mumbling but lovable old goof MTV viewers came to know and love. In his place was the goddamn Prince of Darkness, bellowing out lyrics with crystal clear diction and sporting a madman's gaze to match it. 

On other songs, though, Ozzy fell flat repeatedly. "Into The Void" was filled with missteps as he looked constantly out of breath. But even during his vocally weaker moments, Ozzy's an absolute joy to watch. He paces across the stage hunched over, a short and rapid gait skittering across the Bowl as he pumps up the crowd.

"Fuckin' A, man," he blurted out on more than occasion as he looked at his surroundings in awe. At the start, Ozzy clutched his microphone as he jumped up and down, as if he risked falling over and breaking something if he let go.

By the end, he was hopping up and down, doing the best frog imitation that his body would let him. It was a 21-year-old rock star in the body of a 65-year-old, with Ozzy displaying why he's a card-carrying member of the Screw Getting Old Club. 

Geezer Butler was a nice contrast, rarely moving from his spot onstage and playing his bass with a sense of dignity befitting an elder statesman of metal. Iommi played with a similar air, yet carried a far more imposing presence. He sauntered across the stage with his leather jacket and Gibson SG, the stage lights casting dramatic shadows on his face as he played the infamous tritone on "Black Sabbath" that gave metal the title of "Devil's Music." There was no need for Iommi to do any Springsteen knee slides or Townsend windmills or even turn the guitar vertical. Iommi's legacy allowed him to be the biggest rock star imaginable with seemingly little effort.

Compare this with the band's current touring drummer, Tommy Clufetos. He may be recognized by those familiar with Ozzy's solo work, but probably won't ring a bell with the layman. So Clufetos has taken this opportunity to make a name for himself, flailing his arms wildly around his drum set and making the camera next to it go haywire with every strike of the tom-toms. The original lineup then left the stage halfway through the set to let Clufetos drive the crowd wild with an extended drum solo. 

For anyone born in the last 35 years, this was the kind of show that was once only the stuff of dreams. To see Ozzy grace the stage with his original mates, playing new material and having the time of their lives was truly a once-in-a-lifetime opportunity. For all anyone knows, Father Time could finally win out, making this show the last time Black Sabbath ever plays on American soil, a happy ending to a 45-year career that has been simultaneously magnificent and turbulent. In fact, Ozzy even alluded to this as he addressed the crowd.

"Are you all having a good time, Hollywood?!"

*CHEERS*

"You want us to come back and do it again?!"

*LOUDER CHEERS*

"Well, maybe. We'll have to see what the next chapter holds…"

Read more of NT's show reviews here.

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