The video of this song shows a monster chasing a firefly at first.
Eventually, the monster catches the firefly, he puts her in a cage.
He realizes then that the firefly is sad, is losing her shine.
He releases the firefly, and then he finds a lot of more fireflys.
That's all I remember.
Edit: @kl78 It was an indie/smooth-rock song, in english, with a male singer. I saw the video in youtube, 2011-2012.