The Albiceleste go into Sunday's showpiece having progressed after beating the Netherlands 4-2 on penalties in the semi-finals and are looking to win their third World Cup and their first since 1986.
Germany are highly fancied following their 7-1 demolition of tournament hosts Brazil in the previous round, but Messi has looked to inspire his compatriots ahead of the rematch of the 1990 final.
"Tomorrow, we will play the most important match of our lives for our country," the 27-year-old wrote on his official Facebook page on Saturday.
"My dreams and my hopes are being fulfilled due to the hard work and sacrifice of a team that has given everything from match one."
Many thousands of Argentina supporters have flocked to Rio in expectation of victory and Messi, who has scored four times in the competition so far, is desperate to make sure they do not leave disappointed.
"We knew it was possible [to reach the final]," the Barcelona forward continued.
"Our people, the Argentines, they have carried us here. But the dream is not over yet. We want to win, and we are ready!"