One good song that can relate to Mercutio's death in Act 3, Scene 1 is "I Grieve" by Peter Gabriel. This song perfectly captures the shocked emotional state one can be in when someone he/she loves dies. Mercutio is Romeo's best friend and the shock of death is doubled for Romeo because Mercutio died when Romeo was trying to end the fight and save Mercutio, as we see in the lines:
Mercutio: Why the devil came you between us? I was hurt under your arm.
Romeo: I thought all for the best. (I.iii.102-104)
The lyrics in the song that best relate to the shock of death are:
The news that truly shocks
is the empty, empty page
While the final rattle rocks
Its empty, empty cage....
The image "final rattle rocks" can refer to the last breath that is drawn, capturing the image of the final breath ratteling in a person's rib cage. The image can also capture the image of Mercutio dying and taking his own last breath.
Also, the lyrics that can best describe Romeo's shock and need to process Mercutio's death are:
It was only one hour ago
It was all so different then
Nothing yet has really sunk in
Hence we can see that a song about how suddenly death can overtake a person and how traumatic an experience death can be for the survivors can easily relate to the suddenness of Mercutio's death and how Romeo will grieve over losing his best friend.