Anything written within the last 90 or so years is likely copyrighted. I used the lyrics of an old song in my MG, and because it was in the public domain - written in the 1920s, with a dead composer/lyricist - it was fine. I checked to make sure it was in the public domain before I used it. I also used lyrics for 'fictional songs' from the 1940s and later, but I made up my own words to them. I am also a vocalist/musician/songwriter. I did this so that I didn't have to worry about getting permission.
So, if you want to quote a current pop song, you, or your editor, will have to get permission. If you want to quote something written in 1740, look it up and see if it is in the public domain. It probably will be, and you are free to use it. Always check, no matter what year it was written. Family members will sometimes get something under copyright even if it is old.
Edited to add: I meant to say "publisher" not "editor". Also, make sure your publisher is okay with getting permission and using this sort of material and let them know if something you use is not in the public domain. Some things will be obvious, like a current pop song, but unfamiliar lyrics may not be so clear. They may think you wrote them, so always communicate.