As of this week, Metallica's self-titled 1991 album (often called the "black album" because of its cover art) has sold over 16,002,000 copies -- the most in U.S. history since album sales were tracked by Nielsen's Soundscan.

Sure, artists like Michael Jackson and The Eagles have sold way more albums, but Soundscan introduced the most accurate method for measuring real sales. That means Metallica's "Metallica" album is the best-selling in the past 25 years and the best-selling album properly tracked.

On its way to reaching this milestone Metallica overtook Shania Twain's "Come on Over" album back in 2009.

It sold 3,000 copies just last week!

Billboard has used the Soundscan measurements since 1991. On Billboard's top 200 chart, "Metallica is currently at No. 144 -- its 307th week on the cart. That's the longest run of any album since 1991 and the sixth-longest run since Billboard started in 1956.