Generating enthusiasm:There is every reason to look at songs which they enjoy and take exactly the same approach as we have with our folk and contemporary songs. The opportunity of making comparisons should not be missed.
Important note: Watch the language as many modern songs have meanings which are thinly veiled if at all and might be inappropriate.
If students enjoy singing they should be encouraged to do so. Within every lesson there should be time for them to sing their favourite(s).
Often students are reluctant to sing so I would ask them to 'say the song' in rhythm. Often they will end up singing anyway, avoiding any kind of confrontational situation.
Remember, students have a limited attention span so give them variety within the lesson.