*The police car passes by and drives away. Walt lowers the mirror above him and finds the keys to the car. He starts the car and music starts playing.
The song is El Paso by Marty Robbins which references the name Felina, the title of the episode. Also a song that is on the Marty Robbins Greatest Hits cassette that drops out of the dash
From this point on, everything seems to work in Walt’s favor. He gives Skyler/Marie closure with Hank, he frees Jesse, he kills Lydia/the Neo-Nazis, and gets to die how he wants to die. One interpretation of this is that Walt actually dies in the car and from the keys dropping onward is all a dream/fantasy of Walt’s that plays out for the audience. Read more on that interpretation here
Interestingly the car keys have a Narcotics Anonymous Keychain on them.
To help improve the meaning of these lyrics, visit "Felina" by Breaking Bad (Ft. Vince Gilligan) and leave a comment on the lyrics box