The 36-year-old banged in a double in the first half of Inter's 4-0 win against Atlanta in the Leagues Cup at the DRV PNK Stadium.
He scored his first goal in the eighth minute after being expertly picked out by ex-Barcelona teammate Sergio Busquets.
Messi raced clear on goal as ex-Aston Villa goalkeeper Brad Guzan raced out, but his effort smashed against the post.
Thankfully for Messi, the ball rebounded back to him, where he had the simple task of tapping home into an empty net.
After taking the applause from his teammates, he did his usual 'point to the sky' reaction.
READ MORE ON LIONEL MESSI
Messi making Inter Miami place for celebrities and even Man United are losing fans
Footage shows Lionel Messi comforting DJ Khaled's crying son before Inter Miami heroics
He then locked eyes with Inter co-owner David Beckham to perform the 'hold my beer' celebration, with the 48-year-old seen loving it by the sidelines.
Just like Beckham, Messi was all smiles as he held up his hand in the air where he mimicked holding a pint.
Messi then doubled his tally in the 22nd minute - his third goal in just his second outing for the MLS side.
Again his goal came from close range, as he swept home into the bottom right corner after Robert Taylor found him unmarked in the box.
Most read in Football
Bayern step up plan for Kane, Henderson closer to exit, Liverpool want Lavia
Henderson spotted filming 'goodbye video' ahead of Al Ettifaq transfer
In-demand Ward-Prowse left out of Southampton friendly squad due to knee injury
Fans surprised by Maddison's 'sensational' singing voice in Tottenham initiation
But it was his new celebration that sent social media into meltdown, as one Twitter user said: "Messi doing the 'hold my beer' celebration, looking at David Beckham, so cold."
Another posted: "You just know Lionel Messi is having fun when he cooks new celebration."
A third added: "This Messi's hold my beer celebration with David Beckham is so cold and we love it."
This fan then messaged: "This guy is having the best time of his life. Just playing for fun. No cares or worries in this world."
While another simply stated: "This new Messi Celebration will go viral."