It's great to use songs in the class, if only to do something a little different. But beyond using them solely to give your students some 'light relief', there are many other ways songs can be used in ESL classrooms to consolidate what students have already learnt.
Here are some ideas for the use of songs in the ESL class:
Filling in the Blanks
Songs are often used in this way in the ESL classroom. You can carefully choose which words to blank out depending on what lexical area you want your students to work on.
Instead of doing your usual listening comprehension out of the course books, do a song instead. Get your students thinking about the subject and do any pre-teaching of vocabulary as necessary. As with standard listening comprehension, there are a variety of exercises that you can do with songs: true or false, matching exercises, open comprehension questions, etc.
You can use a song with a clear rhyme pattern to do some phonetics work on particular phonemes.
Strips of Paper
The lyrics you will find on this site can be cut up into strips which then need to be reconstructed as the song unfolds. Alternatively, each student is given a strip to memorise beforehand and the students then work among themselves to 'physically' rebuild the song.
Some songs lend themselves well to vocabulary work. When possible, I have noted on the menu pages when vocabulary exercises are possible.
With some of the songs, I have included a couple of suggestions as to how they can be used but everyone will find something different in each song worth doing.
Of course, you can always just do the songs with your students for the sheer pleasure of it. *_^