The MLS outfit finally confirmed the arrival of the 36-year-old on Saturday, with the forward penning a deal until the end of 2025.
Miami supporters were made to wait to give Messi a hero's welcome as downpours of rain and lightning left the ground soaked.
But not even the horrible weather could ruin the occasion, as Messi - Inter's new No.10 - and the fans were all smiles as he walked onto the pitch to be presented.
A huge catwalk was laid out for Messi, where he was greeted by Inter's managing owner Jose Mas and co-owner David Beckham on the half-way line.
He has become the highest-profile player to make the move to MLS - 16 years after Inter co-owner David Beckham joined LA Galaxy.
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And 2022 World Cup winner insisted he cannot wait to get started, with Inter desperately needing some inspiration having failed to win in 11 games.
Speaking to the supporters, Messi, who was joined by his wife Antonela Roccuzzo and their three sons, said: "Thank you very much, good night.
"First of all I want to thank all the people of Miami for this welcome, this affection.
"I am very happy to be here, to be with you. I want to thank Jose [Mas] and David [Beckham] for the welcome.
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"They are making everything easy for us, everything has been spectacular since we arrived.
"I really want to start training and compete. I want to win, for the club to continue growing. I hope that you will join us as we have since the season began. I thank my new colleagues for the welcome.
"I am very happy to have chosen this city with my family, to have chosen this project. I have no doubt that we are going to have a good time. Thank you all very much for this day."
Labelling Messi's arrival as a 'dream come true', Beckham stated: "Ten years ago, I started my journey to build a new MLS team.
"It's always been a dream of mine to bring the best players in the world to the club and the great city of Miami.
"Players who shared our ambition to grow soccer in this country, who would inspire the next gen' and help build a legacy in this sport, joins our family.
"Please forgive me for feeling a little bit emotional tonight. It really is a dream come true to welcome Lionel Messi to Inter Miami.
"Leo we are so proud you have chosen this club for the next stage of your career. Welcome to the family."
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Prior to Messi's unveiling, Inter also presented Sergio Busquets to the fans, with the Barcelona legend reuniting with his ex-teammate in America.
The duo, who could make their debut against Mexico's Cruz Azul in the Leagues Cup on July 22, will be managed by former Barca boss Gerardo Martino.