MANSFIELD, Mass. — Ozzy Osbourne’s an iffy singer, but a great patriarch.

His singing is technically suspect under the best circumstances, and fighting a throat infection last night at the Tweeter Center, it was downright awful. And the nine hours of bands that preceded him at Ozzfest demonstrated that his music doesn’t even really qualify as heavy metal anymore.

Yet there was the man who made it all possible, singing the songs that made it all possible — solo songs such as “Bark at the Moon” and “Crazy Train,” Black Sabbath classics such as “War Pigs” and “Paranoid,” as well as a few from his new Black Rain album — demonstrating the gleefully anarchic attitude that made it all possible, and the sellout crowd at the free concert ate it up. Even power ballads such as the new “Here for You,” anathema the rest of the day, led to displays of cigarette-lighter solidarity.

Perseverance has its value. In 1980, no one was proclaiming Ozzy Osbourne a founding father of anything. Yet here he is, stumbling around the stage, squirting the audience with foam and water, clapping to no beat having anything to do with the song, and there is, in fact, something lovable about it.

The rest of the fest outlined the state of today’s metal. The basic formula took pummeling double bass drums, added guitars either beefy or tinny, singers either growly or shrieking, and letting the cumulative effect of the 14 bands (besides Ozzy) work its gathering-of-the-tribes magic. That’s not to say some bands weren’t more successful at it, or more distinctive than others. Some groups attacked with enough speed and precision to generate the requisite awe; others tried to cover.

Lamb of God, who directly preceded Osbourne, delivered a top-volume set of “pure American metal” with muscular vocals and guitars reminiscent of Pantera. The speedy guitar riff opening “Walk With Me in Hell” was an impressive touch.

Lordi, best known as the Finnish metal band that won the Eurovision Song Contest, were more Eurovision than metal. Elaborate costumes and masks recalled a cross between Big Nazo and GWAR, and shot sparks from pretty much everywhere — drumsticks, guitars, a chain saw, an umbrella, an 8-foot scepter and seemingly the entire stage. It almost distracted from the fact that, with processed guitars and icy synths, the music was basically Winger. Static-X, who followed them, were undistinguished melodically, but mixed guitars and synthesizers to more aggressive effect, particularly on “No Submission.”

The aggressively anti-religious Polish band Behemoth, one of the European representatives on the second stage, put on an impressive display of speed and power. They mixed black metal and death metal with rapid-fire double bass drums (particularly during a brief drum solo) burping in time with crunching guitars, often playing Phrygian riffs, and throwing in interesting tempo shifts in “Conquer All.” Devildriver seemed to put together all the elements that previous bands had hinted at, with a controlled chaos on most of their intros and choruses and piercing vocals that set the several mosh pits into a fury.

Daath, originally from Boston, were, like Behemoth, chilling in their seemingly unnatural speed and power. In This Moment had moments of power, but used them in the service of a basic arena-rock songwriting aesthetic, the single “Beautiful Tragedy” with its U2-style guitar intro being a good example.

Hatebreed, from New Haven, Conn., headlined the second stage and mixed hardcore punk and thrash with their metal, giving more beef to the guitars and growl to the vocals (without delving into Cookie Monster territory).

rmassimo@projo.com