It's "Sugar" and it's from V, the band's fifth studio album. What can I say? I love the song but the video is amazing as it involves weddings. Granted, it involves the band crashing weddings by performing at them but the couples at said weddings appear to be delighted by the arrival of the band. It has been suggested that some of the weddings might have been staged (although it's also been confirmed that some were indeed genuine) but regardless, the concept of happy couples should be pleasing.
The Wikipedia article for "Sugar" has a large and well-sourced section about the music video. Honestly, I love this song and its video; I'm surprised I hadn't written about them earlier.