The two superstar acts were co-headliners for the final night of the pop festival and, the 'Rockstar' rapper - who closed the weekend with a stunning set - surprised fans during the 'Stressed Out' duo's thrilling show when he appeared unannounced with an acoustic guitar for a rendition of the iconic Oasis anthem.
Malone - who will be releasing his third LP on September 6 - walked on stage in the middle of a piano-led performance of the track, strumming the guitar and delivering a show-stopping vocal performance.
Meanwhile, Friday night (23.08.19) headliners Foo Fighters also gave the Leeds crowd a treat when frontman Dave Grohl brought out his daughter Violet, 13, for a touching duet of 'My Hero'.
The rockers delivered a powerful hit-filled set with some deep cuts, and even played an impromptu cover of Queen and David Bowie's classic 'Under Pressure' after spotting a man dressed as Freddie Mercury and pulling him out of the crowd.
The 1975 played to a huge gathering at the main stage on the Saturday (24.08.19), while Bowling For Soup had people spilling out of The Lock Up tent as they proved their status as pop punk legends.
Billie Eilish flaunted her pop superstar credentials as she looked unfazed by drawing one of the weekend's biggest crowds on Sunday (25.08.19) afternoon.
Elsewhere over the weekend, the likes of Enter Shikari, Frank Carter & The Rattlesnakes, Patent Pending, Mayday Parade, The Hunna, A Day To Remember and You Me At Six entertained the masses.
Carter - along with N.E.R.D. and Bring Me The Horizon - delighted fans with secret sets at last year's festival, and there were a few surprises this time round.
Bullet For My Valentine only treated the Reading site to a performance and Enter Shikari player a third acoustic set down south to break the record for most sets over both festivals in a single weekend (five).
Up north, Drenge pulled a huge crowd at the BBC Introducing stage, while Billy Marten was another surprise as Sherlocks played on both sites after teasing the slot days beforehand.
His new album Underneath It All is out now.