"Beautiful," he said of his swirling strike from outside the penalty area in front of 80,000 people at Wembley.
"I have never scored a goal that went so close to the top corner. That goal represented everything we tried to do today because I fought for the ball, I got it back and I shot with all my strength."
The 3-1 victory over Japan capped a turnaround for Mexico after a disastrous Copa America last year, when the team scored just one goal and went home winless. Peralta was a second-half substitute in those games. He has started each of the four games at the Olympics so far — and now knows he has at least two more games to shine.
"I am very happy to reach the final. It's thanks to a team effort, our families and to God. We can beat whoever we play," he said.
Mexico now plays either Brazil or South Korea in Saturday's final. Mexico's previous best showing at the Olympics was in its 1968 home games, when the team was beaten 2-0 by Japan in the bronze medal match. Japan, which had yet to improve on that performance, will play Friday for a bronze in Cardiff, Wales.
"Mexico is a football nation. They must be partying tonight," coach Fernando Luis Tena said.
Japan, which beat Spain in its opening match, opened the scoring with a good strike from Yuki Otsu on 12 minutes.
The forward sent a swerving shot into the roof of the net from outside the penalty area after several quick passes had carved out a sliver of space for him. Mexico should have been aware of the danger, as a few minutes earlier Hiroshi Kiyotake had flashed a shot past the post from a similar position.
But Javier Aquino was causing problems for the Japanese on the right, and provided a good chance for striker Giovani dos Santos on the half-hour mark, but he shot wide. Not long after the scores were level when Marco Fabian headed in his first goal of the tournament from close range after Japan had failed to clear a corner.
"The goal had to come and what a moment for it to happen," he said. "The fact that it happened at such a special place like Wembley and that it helped us guarantee a medal, made it all a little bit better."
Japan was sluggish in the second half, and struggled to keep possession.
Twenty minutes in, Peralta won the ball off Japan defender Takahiro Ohgihara, who lingered too long after keeper Shuichi Gonda had rolled it to him. Peralta briefly ran with the ball, then shot high and to the left of Gonda. Deep in added time, substitute Javier Cortes ran onto a Peralta backheel, beat a defender and then shot under Gonda to seal the victory.
"We had a good start, but then stopped moving," Japan coach Takashi Sekizuka said. "Everyone is very disappointed. But we need to get over our emotion and prepare for the next game."
Tena praised the squad for rebounding after the Copa America in Argentina.
"We clenched out teeth and moved forward. I am surrounded by great people, they are always working," he said. "The players want to sign contracts abroad, it is a fantastic moment."
Tena said the team wouldn't settle for silver.
"We want a gold," he said.