Metallica had sold 16.4 million copies in the United States by 2016, according to the album’s documented sales figure.
That total made Metallica the best-selling album in the United States since Nielsen SoundScan began tracking sales in 1991. SoundScan’s introduction made it possible to measure sales using electronically collected retail data, providing a more consistent picture of the US market.
The album’s sales were spread across several formats. By 2016, about 5.8 million of the US copies had been purchased on cassette, an unusually large share that reflects the format’s popularity during the early 1990s. The album continued selling steadily long after its initial release.
The figure is a historical 2016 measurement, not a claim that sales stopped there. Later certifications and updated totals can differ depending on whether they count shipments, sales, downloads, or streaming-equivalent units. The 16.4 million figure specifically refers to the documented US sales total at that time.