The pentagram has a very long history that is now admittedly skewed. Technically, a pentagram is drawn with five straight stokes and creates a pentagon in the center. The star alone is also known as a pentacle or pentangle. The pentagram has been used in a myriad of religions including Christianity and Wicca, but it's use in Satanism has essentially robbed the symbol from any other association.
Metal music has used the symbol to the point where it's a laughable cliché, however non-metal bands have also used it. Please add any albums that have a pentagram on the cover and are not included here to the comments.
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I suppose if you are going to do a list of album covers that have a pentagram on them you need to start it with The Satanic Mass as performed by the founder and High Priest of the Church of Satan, Anton LaVey. I haven't personally heard the record, but I am sure it's a combination of dark creepiness and campy hilarity.
Although not a true pentagram, the cover of 2112 was mean to combine the witchy, supernatural feeling of the occult with space age science fiction. Released in 1977, 2112 is one of the pinnacle moments in prog rock and is the first pentagram-laced album I ever saw as well as the first I ever bought.
Although the cover of "Shout At The Devil" was later changed to feature the mug shots of the 4 band members in full glam mode, originally it was a simple matte black background with a glossy black pentagram. Kind of like Spinal Tap, but for real. I still think this was the Crue's best album, but it was downhill from here.