What's the best way to guarantee your fans stay happy when you're getting ready to release a new album that deviates from your usual sound? There aren't any hard and fast rules, but you could do a lot worse than the approach Metallica took for their self-titled "black album" in the summer of 1991.

Aware that they'd taken a tighter, more mainstream approach on the LP and eager to make the biggest impression possible, the group scheduled a free preview at Madison Square Garden on Aug. 3, 1991, giving away a reported 19,000 tickets through a special promotion at the Wiz music store chain. The result, as MTV News reporter Tabitha Soren predicted in the footage above, "probably set the record for being the largest listening party ever."

A quarter of a century after the album in question topped the charts and cemented Metallica's status as one of the world's biggest rock acts, the idea of the group going to such lengths to promote a new release might seem a little strange. But at the time, though they already had some platinum under their belts, the band's team knew they could get a lot bigger with the right amount of exposure.

"Metallica was already a very big act, bigger than a lot of people comprehended," explained manager Cliff Bernstein. "[They] sold 2.6 million copies of ... And Justice for All, and the band never got a lot of radio play and had only made one video. We wanted to get to No. 1 on the charts right away. That would convince the industry that they're missing something if they don't latch onto Metallica."

Watch an MTV Report About Metallica

It obviously worked, but it was still a gamble. As frontman James Hetfield later explained, he even sneaked out on the floor during the listening party so he could get a firsthand view of the crowd's response to the record. "I had to run out there and see what they thought — if they were killing themselves or killing each other. Or falling asleep," he admitted to Rolling Stone. "They were really attentive. They were really listening to what it said."

When they weren't busy rocking out, that is. "With the opening moments of [Kirk] Hammett's immortal riff, Lars [Urich]'s soul groove pounding — at once thunderous and rhythmic, and [Jason] Newsted's propulsive bass," wrote David Masciotra in his 33 1/3 book on the album. "The 10,000 metal acolytes who filled the arena jumped out of their chairs, flashed devil horns, banged their heads and played air guitar."

The audience's response was merely the first wave in an incredible deluge of sales, awards and critical acclaim. By the time the Metallica record had run its course, the band was hailed as the most triumphantly successful example of metal's move to the mainstream. And it all started with a party — even if it meant, as drummer Lars Ulrich later quipped, "Our album played the Garden before we did."