The Argentine superstar found the top corner with a second half set-piece to clinch a surprise victory for the MLS side and give them a strong chance of progressing from Group A.
Inter Miami and Palmeiras have four points each, after the Brazilian side beat Al Ahly 2-0 earlier on – the Egyptians, like Porto, have one point.
Samu Aghehowa’s early penalty gave the Portuguese side the lead as they had the better of the first half and could have scored more.
However Telasco Segovia blasted Miami level and then Messi’s free-kick helped them claim a noteworthy scalp, in a match many thought would be straightforward for Porto.
“It’s a huge joy, the whole team made a big effort, we worked really well,” Messi told DAZN. “It’s a really important win for us and we have to enjoy it.”
Even with Messi, the Mercedes-Benz Stadium was under half-full at kick-off, hamstrung by another 3:00pm kick-off on a working day as it was for Chelsea’s opener against Los Angeles FC at the same venue.
More fans entered throughout the game, with nearly 32,000 present in the end. (AFP)