I'll Call You Mine (And I'll Be Yours) [Merlin, Merthur]

I'll Call You Mine (And I'll Be Yours) by Chechilia

When Uther calls to ask Arthur his plan for his wedding with Elena, it's Merlin, Arthur's boyfriend of two years, that receives the message first. And when Arthur comes back home, he finds the flat empty. 

You wanna cry and be all sad? This is for you. This fits perfectly if you are sad and lonely and all you wanna do is cry and stay in bed feeling sad. This will help with all that.

Happy ending is just a bonus point and the reason to believe that there is tomorrow.