Answer by taking a quote from the following article:

Anberlin was an American alternative rock band formed in Winter Haven, Florida in 1998 and disbanded in 2014. Since the beginning of 2007, the band consisted of lead vocalist Stephen Christian, guitarists Joseph Milligan and Christian McAlhaney, bassist Deon Rexroat, and drummer Nathan Young. Members of Anberlin originally formed a band under the name SaGoh 24/7 in 1998, releasing two studio albums before disbanding, with the members having a change in musical direction and name. Anberlin was formed in 2002; within a year of forming, they had signed with semi-independent record label Tooth & Nail Records and released their debut album, Blueprints for the Black Market.

Over the years, many fans, critics, and other members of the media have consistently characterized Anberlin as a Christian band. However, Stephen Christian stated in an interview that their faith is more complicated than a simple label: "I think we're categorized like that a lot because we're on Tooth & Nail Records, which, years ago, was known as a Christian label and never lost that reputation. I don't care who listens to our records. If it helps people in whatever circumstances they're in, that's amazing, but I definitely don't classify us as a Christian band." Elsewhere, Christian has remarked, "[My faith] affects every single aspect of my life, but I'm not a preacher, I'm an entertainer."  Despite these statements and others of the like, multiple sources list the band as part of the Christian rock genre, and some Anberlin song lyrics do contain Christian references. Furthermore, the band appears at Christian music festivals such as Parachute Music Festival and Cornerstone Festival, and their songs have been included on Christian rock compilation CDs and DVDs. They are also played on the Gospel Music Channel.  Anberlin has also been repeatedly featured in Christian rock magazine HM (Hard Music, which was originally the fanzine Heaven's Metal). Christian submitted a letter to the magazine, criticizing the more overtly religious Christian punk band the Knights of the New Crusade for a promotional image that represented a "black mark on the face of Christianity".  Christian has also said in an interview with Lightforce radio how the band tries to "step out of the bubble" and referred to themselves as being part of Christian music. He discussed in detail what Christians should do in their lives: love and embrace others as Jesus would as well as show God's grace to others. He mentioned as well how the band Fall Out Boy said in an interview that they did not really know much about Jesus until Anberlin toured with them.  In an interview with Smartpunk, drummer Nathan Young commented, "The thing is, some bands that are trying to get out of the Christian market, they get bummed out by questions about it. I don't really mind it, because I'm a Christian, and I'm okay talking about it. With the whole term 'Christian Band,' I don't understand how a band can be Christian. We get the question, 'Is Anberlin a Christian band?' and it's like, yeah, Anberlin is -- as humans".

Do they sing about christian things?
"[My faith] affects every single aspect of my life, but I'm not a preacher, I'm an entertainer."