When someone gives there life to Jesus....it's a huge deal to the angels. Their celebrating and rejoicing for that person because they finally came home to the father...and escaped the torments of hell prepared for the devil and his angels. I gotten saved when I was 11 about 4 years ago this is what I pictured was happening. My idea of angels rejoicing involves dancing, happy music, and LOTS of colorful fire works...well that's me.
P.S - sorry about the angels...they look like teenagers lol