What makes Sad but True by Metallica notable?

This album is significant for featuring 'Nothing Else Matters,' which became a crossover hit, showcasing Metallica's ability to blend heavy metal with more melodic elements. Additionally, the album's themes of despair resonated widely during the early 90s, contributing to its enduring legacy within the rock genre. By the time 'Sad but True' was released in February 1993, Metallica was at the peak of their commercial success following their self-titled album (often referred to as 'The Black Album') in 1991. The band had transitioned from thrash metal pioneers to mainstream rock icons, navigating the complexities of fame and artistic integrity during this period.