Music: Iron Man (The Cardigans cover)
When a band covers a song, they can either remain faithful to the source material or depart radically away from it. How different a cover actually is depends not on any changes in tone or style, but on the musical variations a cover brings to the table. Seether's version of George Michael's pop classic "Careless Whisper" introduces grungy guitars and angrier vocals, for instance, but otherwise stays pretty close to the original.
For something that strays a bit further, here's an excerpt of a live concert by The Cardigans, where they perform their cover of Black Sabbath's "Iron Man" (you can find the recorded version on their third album, "First Band on the Moon," which also contains the megahit "Lovefool"):
While the lyrics and overall structure are pretty much unaltered, many of the details have been changed. The band messes with the song's distinctive guitar riff, adding some jazzy notes to the straightforward heavy metal progression. The rhythmic drones of the keyboard gives some background texture to the song's verses (the original, like most early Sabbath, had Ozzy singing with the "Iron Man" riff throughout), and between verses, frontwoman Nina Persson inserts the occasional vocal flourish. Taken as a whole, you have a great cover that respects the original without being enslaved by it.