In March 2018 Amy Shark provided, "Sink In", for the film soundtrack of Love, Simon. The related album, by various artists, debuted at No. 37 on the Billboard 200. In the following month she performed at the Commonwealth Games closing ceremony on the Gold Coast, in a duet with Archie Roach and an indigenous youth choir for a rendition of Roach's "Let Love Rule".
On 11 April 2018 Shark premiered a single, "I Said Hi", on Triple J before releasing it the following day. It received unpaid promotion by comedians, and digital radio show hosts, Luke and Lewis using posters, megaphone and a large home-made sign hung up next to the Fox FM Melbourne station logo. That promotion captured the attention of the singer-songwriter who displayed it on her own Instagram account. "I Said Hi" peaked at number 6 on the ARIA charts.
Shark's debut album, Love Monster, was released on 13 July 2018 and it debuted at number 1 on the ARIA Charts. The album provided four additional singles, including "Mess Her Up" (March 2019). At the ARIA Music Awards of 2018, the artist won four ARIA Music Awards, with Album of the Year, Best Pop Release and Best Female Artist for Love Monster, and Producer of the Year for Dann Hume and M-Phazes work on "I Said Hi". She was the most nominated artist and equal highest winner in that year.