"For Good" is a musical number from the hit musical Wicked. It is sung as a duet between Elphaba and Glinda as a farewell. The song's score and lyrics were written by composer Stephen Schwartz. From Wikipedia
A 20-second teaser spotlights Elphaba’s and Glinda’s new looks with a brief melody from their duet “For Good”, priming audiences for June 4’s full trailer
