How do I write a song?

If you had to write a song about a certain subject, how would you do it?

• I have to write a song for a certain unit in school and present it. I don't know how to approach it, should I choose a song I want the music for then just change the lyrics? If so, how should I change the lyrics (do I need to have the same amount of syllables per line, does every line need to end with the same sound, etc.) ? Or should I just write the song, then choose music, and if so how would I get my song to fit the music? Thanks in advance!

• Answer:

  You should choose the music first. Something that'll get the class ad teacher hooked. Then take your topic and make a poem about it, but have it in rhythm to the beat. Once you start, it won't seem so hard. Trust me. You're thinking too much