Lions are the most social of cats, living in groups called prides. In these prides, whenever another male takes over, it kills the other male's cubs. These less-than-noble traits are ignored in folk mythology, heraldry and the Narnia book series, where Jesus is represented allegorically by a lion named Aslan.
Lions often feature in Christian stories, but are still noticeably absent from the New Testament (except as the symbol of one of the gospel writers (Mark)). They do turn up in the Old Testament a couple of times. Lions are used by God to kill several people personally. In 1 Kings a prophet is killed by one for believing another prophet, and a man suffers the same fate for refusing to strike a prophet. Several foreigners are killed by lions in 2 Kings for not worshiping God. The lions don't get it all their own way in the Bible, however - David and Samson kill one each, the latter lion being torn open to house a swarm of bees.