Check out the Bruno Mars website. Where they state :
We’re happy to announce exclusively on BrunoMars.com that Bruno’s new song “It Will Rain” will be featured on The Twilight Saga: Breaking Dawn – Part 1 Original Motion Picture Soundtrack.
“It Will Rain” will be available worldwide* exclusively on iTunes this Tuesday, September 27th.
*UK single will be available October 31st.
The soundtrack album will be available everywhere November 8th.
Come back to BrunoMars.com this Tuesday (9/27) to hear ‘It Will Rain’!”