This scene heartwarmingly shows Merlin and Arthur's friendship.
The line "I had know idea you were so keen to die for me" was one of my favourite quotes.
. . . by William the rocket scientist, Arthur the Brad Pitt or Lancelot's car. XDDD
As someone had commented before, the song relates to how Arthur was physically able to awaken Merlin from the poison, saving his life and how Merlin was emotionally able to awaken Arthur from his pride, thus allowing him to begin to become the king Arthur is meant to be.
The clips matched so well with the video. I couldn't help but laugh.