As far as "secular" music goes, there are a lot of Christians in metalcore bands. There are also a fair number in the progressive metal circles as well. Its not completely uncommon to find Christians in Gothic/Doom Metal bands these days either. While most melodic death metal bands don't seem to be flowing over with christians, most of them lyrically deal more with social themes, personal struggle, introspective thought, war and death as a societal effect, dark fantasy, and occasionally touch on spiritual issues.
As I Lay Dying have members with strong christian beliefs, but consider themselves to be a metal band that isn't so much "Christian" as that God has positively influenced the lives of its members and the lyrics reflecting this.
Killswitch Engage also touched on a theme central to Christianity, forgiveness in the song "starting over". While some members appear to have Christian beliefs, again they are not a group I would consider as "Christian Metal".
As for progressive metal, Neal Morse, Dream Theater, and Queensryche all have pro faith songs in their catalogue. Dream theater however is more critical (as a band) of organized religion, but their lyrics at times are supportive of having a relationship with God. Dream Theater's "I Walk Beside You" has a particularly pro God tone in that it calls the weary believer to cast their cares to God. However, "blind faith" seems to deal with people following God that are spoiled and expect God to do more for them and the world arround them. It seems to question why God doesn't do more, but the song is part of the 6 degree of inner turbulance album, which the struggle of faith is considered 1 of the 6 degrees. Another song on the album deals with a person becoming humbled and has the lyrics "From a thief to a beggar, from god to God save me".
Within Temptation does a song called "the Cross" and seems to be focused on God's point of view in calling a lost child. However, they criticize religion itself for being the cause of wars on a latter album track.
