As well as never previously winning at QPR, Swansea had lost all their opening-day fixtures since 2005, while many predicted they would struggle following the departures of Brendan Rodgers and Joe Allen.
Michu told Swans Player: "It's been an unforgettable day. It couldn't have gone better. It's my first real game for Swansea City and I scored two goals and started in great shape.
"The most important thing is that the team has won 5-0. It's three points that are going to make us grow and grow into the league."
The 26-year-old added: "It's been such a good start and I didn't expect, first game of the season, to score two goals.
"I hit the crossbar as well and could have got a hat-trick.
"I'm very pleased with the fans as well, I was very impressed, and I hope I'm going to keep going."