Metallica's The Black Album surpassed Shania Twain's Come On Over as the best-selling SoundScan-era album in 2009.
The comparison concerns Nielsen SoundScan sales tracking, which began in the United States in 1991, the same year Metallica was released. By 2009, the album's steady sales had allowed it to overtake Come On Over in that specific era-based ranking.
Metallica's achievement was driven not only by its huge initial success but also by remarkable long-term catalog demand. The album never sold fewer than 1,000 copies in a week and continued averaging thousands of copies weekly even decades after release.
This ranking should not be confused with all-time worldwide sales comparisons. The Dark Side of the Moon and Tapestry remained important reference points for chart longevity, while Metallica's distinction specifically concerned US sales during the SoundScan era.