The above mural that I encountered in Córdoba made me think for days. How do I answer this question: “What is poetry?” This nagging question eventually made me come up with my own personal definition of poetry. To me, poetry is a group of words that can be sung. It must be musical. Does it have to be beautiful? Well, all languages become beautiful when we sing. But at least good poems are the ones that we can sing along. Do they have to follow meter and rhyme schemes? In classical verses such as English sonnet, French alexandrine, or Korean 시조, yes. But for modern poetry, not any more.
Do ALL the poems on earth have to be song lyrics, then? Not necessarily, but poems CAN become song lyrics. Prose and other literary genres, no. Some famous poems have not been put into songs, yet. They just need a talented and motivated lyricist or a singer who can nicely transform them into music.
By this utterly personal definition, all the song lyrics on earth are poetry. Just like this one: