Iron Maiden
Iron Maiden aren't a band I generally think of as epic. They have their moments of almost-but-not-quite, like "Invaders" or "The Trooper", but I see them more as kissing cousins of epic metal. "The Rime of the Ancient Mariner" is the only song I can think of off the top of my head that really qualifies. The long length, the engrossing story, the musical change-ups, and possibly most important, the spoken word interludes with actual quotes from the original poem all make this true blue epic metal of epictastic proportions.
Saxon
Saxon have never even gotten to first base with epic metal. They're a working class biker metal band to the bone. So "Crusader" is really an anomaly in their catalog. I suppose it's the British history aspect, as Saxon are pretty open about their love of country. It makes it slightly embarrassing as a result, since this is not what I'd consider to be... politically correct. It glorifies the Crusaders in a way that is totally one-sided, but it's more in a way that pays homage to their ancestors rather than openly demonizing Muslims. Either way, it's epic as ****. Too bad the rest of the album sucked.
Black Sabbath
This isn't an epic metal song. I'm just including it to show just far back this aesthetic goes in metal. From the first song on the first album of the first metal band this kind of larger-than-life storytelling element has been a part of this music. It just seems to go hand in hand with the escapist, outsider nature of metal. And whether it's sword and sorcery or religion it adds up to similar results. Fantasy and religion both have mythology as a common ancestor after all.