The lead single from the Icelandic rockers' new album, Fever Dream, earned 8.8 million audience impressions, up 9%, according to Nielsen Music.
The song is Of Monsters and Men's first Rock Airplay leader, after the act reached a prior No. 2 best with "Mountain Sound" in 2013. The band also boasts a No. 3 hit in its 2012 breakout single "Little Talks."
Of Monsters and Men becomes the second act to earn its first Rock Airplay leader in 2019, following Shaed, whose "Trampoline" led for three weeks beginning in July.
"Alligator" now has ruled two airplay rankings, having topped Adult Alternative Songs for two weeks in July.