SoundScan began tracking U.S. music sales in 1991. Its point-of-sale data was first used to compile the Billboard 200 albums chart on May 25, 1991. "Metallica" marked the group's first No. 1 that year, when it debuted atop the list.
"Metallica" became the biggest-selling album of the SoundScan era in the week ending Dec. 20, 2009, when it overtook Shania Twain's "Come On Over." Twain's album is currently in second place on the list, with 15.57 million.
"Metallica" and "Come On Over" are the only two albums that have sold more than 15 million copies in the SoundScan era. There have been 22 releases that have shifted at least 10 million. The most recently-released title to reach the 10 million plateau was Adele's 2011 album "21." (Its sales now stand at 10.94 million.)
On the most current Billboard 200 chart, "Metallica" climbs from No. 155 to No. 144, marking its 307th week on the chart. That continues to be the longest chart run of any title since the tally began using SoundScan data.
Since the Billboard 200 became a regularly-published weekly chart in 1956, "Metallica's" run is the sixth-longest. (Pink Floyd's "The Dark Side of the Moon" has the most weeks on the chart, with 861.)