The Italy Under-21 forward has returned from last term's loan moves at Sampdoria and QPR after failing to establish himself at Old Trafford, making only 12 appearances in the last three seasons for the Sir Alex Ferguson's side.
Although the promising youngster's playing time at Loftus Road was hindered by an ankle injury, the former Lazio striker is determined to break into the United first team upon his return.
Macheda told the club's official website: "It's great to be back at Manchester United. When you go on loan you really understand how important it is to play for this club.
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"Last season was disappointing. In the first six months I didn't get a lot of opportunities here so we decided it was best for me to go on loan.
"When I got to QPR things went a bit wrong, though, as I was feeling my ankle a lot. But now I feel a lot better and want to start the season well. It's a big season for me."
The 20-year-old has also spoken of his excitment going into the Red Devils' pre-season tour of South Africa, China and Europe, enthusing: "I'm really looking forward to it.
"It's always great to visit fans in different countries. You meet new people, you see new cities, you experience different cultures.
"I didn't know how big the club was around the world when I went away for the first time in 2009. But I was very impressed by Malaysia, China and Korea.
"We have great support all over the world and I love being part of this team."