Satan enjoys luring good Christian men into the sinful works of the flesh, which is of the devil, and what better way is there to use Metallica, the most popular heavy metal act of all time. Satanic lyrics found in Jump in the Fire, Master of Puppets, and The God that Failed, promote Satanism and are against Christianity.
This is coming from a Metallica fan, but I'll try not to be biased. Basically, barely any of Metallica's songs are about Satan, let alone even mention him. The only one that does is Devil's Dance from Reload, but that is more of a story rather than a demand. Most of Metallica's songs are about personal struggles, literature, politics and other things that don't involve Satan. Very few Metallica songs even involve religion, notable exceptions being Creeping Death (About the Plagues of Egypt from the Bible) and The God that Failed (About the lead singer's mother who passed away from Cancer and refused treatment as she was a Christian scientist). To give more examples for my above points, a lot of Metallica songs are about personal struggles, such as Master of Puppets (Drug abuse), Dyers Eve (Once again about the lead singer's childhood. Along with his mother passing away from Cancer when James was 16, James' father left the family when the former was 13). Additionally, most songs from their often chided 8th album, 'St. Anger' were born from tensions within the band stemming from James going through rehab and their bassist, Jason Newsted leaving the band. A few Metallica songs involve literature, such as For Whom The Bell Tolls (Based on the Ernest Hemingway novel of the same name) and Welcome Home (Sanitarium) (Based on One Flew Over the Cuckoo's Nest by Ken Kesey). A good portion of Metallica's 4th album, '...And Justice For All' is about politics. Blackened is about environmental disaster, the title track is about corruption, Eye of the Beholder is about censorship etc. Additionally, Metallica have numerous songs about other topics. Many songs on their debut album, 'Kill 'Em All' are about the band's live shows, as is the song Battery. Their songs Fight Fire With Fire and Disposable Heroes are about war, Enter Sandman is about childhood night terrors, the songs Fuel is about James' love for cars, the songs The Memory Remains and Moth into Flame are about celebrities who have fallen from grace.