The Icelandic quintet nabs its fourth No. 1 on the chart and first since "Crystals," which ruled for three weeks in June 2015. Its other No. 1s: "Mountain Sound" (three weeks, 2013) and "Little Talks" (four, 2012).
"Crystals" brought Of Monsters and Men's previous quickest coronation: 10 weeks.
"Alligator" concurrently holds at its No. 4 high on the all-rock-format Rock Airplay chart, with 6.7 million audience impressions, according to Nielsen Music. It also spends a second straight week at No. 6 on the Alternative Songs airplay chart, after reaching No. 5.
The track is the lead single from Fever Dream, the band's third studio album, due July 26. Its previous release, 2015's Beneath the Skin, debuted at a career-best No. 3 on the Billboard 200 and has earned 352,000 equivalent album units to date.