Their lyrics are objective. They are just words that can be applied subjectively to apply to Christian beliefs. If you don't believe in Christianity, you can still just listen to them and appreciate their music.
For example, if you are a Christian, their song "Rebirth" would mean about coming to know God. However, if you are not a christian, it can be applied to other meanings, such as getting through hard times and changing as a person.
Just look at the lyrics, it never mentions "God" or "Jesus" even once.