The 21-year-old completed a €57 million move to Camp Nou in June after months of speculation surrounding his future, but Messi believes the Brazil star will have no problem adjusting to life in Catalunya despite the hype surrounding his arrival.
"He is a great player and he will have no problems adapting. He'll have no trouble off the pitch either. He's a good lad," Messi told a press conference on Wednesday.
"He will give a lot to the team. In one-on-ones, he is very dominant. He's going to make a difference."
Messi has already seen two team-mates leave this summer, with Thiago Alcantara joining Bayern Munich after David Villa had signed a deal with Atletico Madrid, and the 26-year-old believes the two clubs have completed excellent business in bringing in the two players.
"Thiago? It was a personal decision, he thought he'd play more there [at Bayern]," Messi explained. "Villa? He's a great signing for Atletico, he's a real goalscorer."
Barcelona suffered a 7-0 aggregate defeat to Bayern in last season's Champions League semi-final, and as a result Messi admits he is fired up for the tournament next season- although he acknowledges the threat posed by the European champions under Pep Guardiola.
"The Champions League defeat from last season is an extra motivation for this year. It's another challenge," Messi continued.
"Bayern already had a great team and with Guardiola they'll be even stronger. In La Liga, [Real] Madrid will be a tough opponent, as always."
Messi was rocked by tax fraud claims earlier in the summer, with the Argentina captain and his father allegedly owing around €4m in unpaid bills, but Messi insists he is relaxed as his advisors continue to handle the proceedings.
"I'm calm. We'll see how things go," he continued.
"I never take care of that stuff myself and neither does my father. We have our lawyers and our wealth managers to take care of that and we trust them and they will sort this out.
"The truth is that I don't have a clue about all this and that is why we have people taking care of it."