It is the first new song by Jackson to be released since his sudden death in Los Angeles on June 25.
The singer, who had not released new material in years, sounds confident on the song, which features his trademark vocal style with lush backing vocals by his brothers, the Jacksons.
It is a mid-tempo number with orchestral backing played during the closing sequences of the documentary, which opens Oct. 28 for a limited two-week run.
"This is it," goes one verse. "Here I stand. The light of the world. I feel grand."
The song will also be part of a two-disc CD set that will accompany the movie in what is expected to be a worldwide marketing blitz.
The documentary features footage of Jackson rehearsing for his planned London concerts, which were to mark his return to the stage after a lengthy absence caused in part by a series of legal and personal problems.
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