1. First of all, many English songs are very particular about grammar and rhetoric, just like poetry, which is the essence of language. Not everyone can write poetry. Similarly, not everyone can write lyrics. Just give two examples:
When I was young, I would listen to the radio and wait for my favorite songs.
No matter what the cost, no matter how my heart is broken, I will wait for you here.
I feel that you have a good grammar foundation, so you can definitely see how many grammatical phenomena, how rigorous and how regular these short lyrics are.
2. The lyrics of backstreet should be imperative sentences to make "everyone" "rock your body". Something like: Mary, sing a song.
With regard to the song "Take me to your heart", I agree with the idea of "recommended answer" at first. Sometimes the melody should be considered in the lyrics, and the word order should be adjusted to match the pronunciation of the melody. Sometimes, in order to rhyme at the end of a sentence, we have to add or subtract words and pronunciations. For example, in a song, california rhymes with [California _ na _ yi _ o]. In addition, I would like to remind you that this song is an English song adapted from Chinese by Danish singing group MICHAEL LEARNS TO ROCK. It is not original in English, nor is it the work of native speakers, so there are many irregular or scattered places in the song.