Just been listening to Good King Wenceslas or In The Deep Mid Winter. The way they are delivered seems to me very similar to rap songs. They have a tempo, albeit weaker, but mostly they tell a story mainly in words.
^Good King Wenceslas looked out, on the Feast of Stephen,
When the snow lay round about, deep and crisp and even;
Brightly shone the moon that night, tho' the frost was cruel,
When a poor man came in sight, gath'ring winter fuel^
It is a song about hardship, like most rap songs. Also this one is very lyrical.
^What can I give Him,
Poor as I am?
If I were a shepherd
I would bring a lamb,
If I were a wise man
I would do my part,
Yet what I can I give Him,
Give my heart^
I could see Post Malone, Eminem or Logic delivering them to a very high standard indeed.