Messi arrived from Beijing at midday on Monday and according to Argentinian media will participate in the national team's next training session later Monday afternoon.
Many were skeptical about the five-time Ballon D'or winner's presence in the June 9 friendly, but promoters will be ecstatic with his arrival four days before the match against old rivals Brazil.
The 29-year-old has been in stunning form for Barcelona this season with 54 goals and 17 assists in 52 games.
Messi has been in Melbourne once before with Argentina, taking on Australia in 2007 at the MCG.
Friday's match will be Argentina's first under new coach Jorge Sampaoli who recently joined after an impressive first season with Spanish side Sevilla.
Messi is not the only big name in Melbourne, with Gabriel Jesus, Angel Di Maria and Nicolas Otamendi all arriving in the past 24 hours.
A near sellout is expected for Friday's match with just a few tickets still remaining.
Goalkeepers: Sergio Romero (Manchester United), Nahuel Guzman (Tigres), Geronimo Rulli (Real Sociedad)
Defenders: Emanuel Mammana (Lyon), Gabriel Mercado (Sevilla), Nicolas Otamendi (Manchester City)
Midfielders: Eduaro Salvio (Benfica), Lucas Rodrigo Biglia (Lazio), Ever Banega (Inter Milan), Manuel Lanzini (West Ham United), Leandro Paredes (Roma), Guido Rodriguez (Tijuana)
Attackers: Leo Messi (Barcelona), Gonzalo Higuain (Juventus), Joaquin Correa (Sevilla), Alejandro Dario Gomez (Atalanta), Mauro Icardi (Inter Milan), Angel Di Maria (Paris Saint-Germain), Paulo Dybala (Juventus)
Goalkeepers: Diego Alves (Valencia), Weverton (Atletico-PR), Ederson (Benfica)
Defenders: David Luiz (Chelsea), Gil (Shandong Luneng), Jemerson (AS Monaco), Rodrigo Caio (Sao Paulo), Thiago Silva (PSG), Alex Sandro (Juventus), Fagner (Corinthians), Filipe Luis (Atletico Madrid), Rafinha (Bayern Munich)
Midfielders: Fernandinho (Manchester City), Giuliano (Zenit), Lucas Lima (Santos), Paulinho (Guangzhou Evergrande), Philippe Coutinho (Liverpool), Renato Augusto (Beijing Guoan), Rodriguinho (Corinthians), Willian (Chelsea)
Forwards: Diego Souza (Atletico-PR), Douglas Costa (Bayern Munich), Gabriel Jesus (Manchester City), Taison (Shakhtar Donetsk)