Please have a look at the sentence below:
This is the popular song of Taylor Swift.
To me, if there isn't any specific song related to that singer known as "popular", the usage of the here is not correct.
The refers to the construct "popular song" here but more to the word "popular". And since apparently there isn't such a specific song known as "popular", we should use an indefinite article: This is a popular song of Taylor Swift.
Using the definite article can be optional in some cases but in this sentence, it's not.
Do you guys agree with me?