The Black Sabbath single that reached the highest position on the US Billboard Hot 100 was “Iron Man.” It peaked at number 52 in 1972, making it the band's highest-charting US single on that chart.
“Iron Man” first appeared on Paranoid, Black Sabbath's second studio album, released in 1970. The song grew from one of Tony Iommi's heavy guitar riffs. Ozzy Osbourne reportedly heard the riff and described it as sounding like “Iron Man,” inspiring Geezer Butler to write lyrics about a time-traveling figure who becomes a metal giant.
The single version was edited substantially for radio, running about 3 minutes and 33 seconds compared with the much longer album recording. It was released in the United States in 1971 and reached its Hot 100 peak the following year.
“Paranoid” is the common answer people remember because it became the band's signature song and reached number four in the United Kingdom. In the United States, however, “Paranoid” peaked at number 61, below “Iron Man.” The track gained another major audience decades later through its use in Marvel's Iron Man films and related media.