I think it really varies depending on the lesson. Like the lesson I'm teaching my Grade 2 middle schoolers this week is based off of the question "What do you mean?" so I started off the lesson with the song What do you mean? by Justin Bieber. All I did was print out the lyrics and had them listen and fill in the blanks for some of the lyrics. It took up the first 10-15 minutes of class. I've been hearing them sing "What do you mean?" in the hallways and at lunch all week, so at least I know they're not going to forget that one! I think that kids love songs that have to do with the lesson because it's easier to remember a song, than boring book work or lectures.

I've seen other people do true false questions or ask for examples in the song that are related to the topic they're discussing for the day. It's all relevant and helpful depending on how long you want to spend during the lesson on the song.