Hello. I started to like Opeth more in the year 2013. The first time I heard Opeth was in 2008, the album Still Life. That album is legendary. It is about a dude, who is banished from his country, and later seeks to find his love, who had become a nun. Then he tries to take her away, but they kill her, because of him, he doesn't follow their beliefs, is probably atheist. It is a true love story, with a sense of hope in the end (White cluster song) where he sees angels, and is convinced that he was wrong (in disbelieving God) and is granted a relief in death he meets God. Anyway, that's how I see this. It is a beautiful story.
Anyways, some say Opeth have satanic songs, but as I read all their lyrics, I find it to be false. They mostly sing about emotions, Nature, love, hate, sorrow, sadness and so on.
For me they are great musicians, and I don't see anything wrong with being a Christian and enjoy metal music in general.
Of course I want to stay away from the Satanic bands like Cradle of filth, Deicide, etc.