Defining metal music is never easy, but for this all-time list, opted to leave bands like Led Zeppelin and Queen in the hard rock camp and concentrate on the heavier metal sounds – Iron Maiden, Sabbath, Metallica and the like.

10. “Breaking the Law,” Judas Priest

Written by Judas Priest’s holy trinity of Rob Halford, Glenn Tipton and K.K. Downing, “Breaking the Law” features one of the most famous opening riffs in metal, and music, history. Released as the lead single off of 1980’s beloved British Steel, the song is a lean, mean classic – coming in at about 2:30 with no solos. Halford later told Billboard that the economic situation in England had an effect on the lyrics. “It was a time in the U.K. when there was a lot of strife,” he said. “That was the incentive for me to write a lyric to try to connect with that feeling that was out there.” And what’s more metal than deciding you’re done with living your boring life and that it’s time to live on the edge? “Breaking the Law” is a metal song that’s so dangerous, you might even be able to rob a bank with it

9. “Hallowed Be Thy Name,” Iron Maiden

Iron Maiden are the kings of the end-of-the-album-side, eight-minute epic and – with apologies to “Rime of the Ancient Mariner,” “Fear of the Dark” and a few others – they’ve never done it better than on this Number of the Beast monster. From the initial bell tolling to the rush of the full-band entrance around the one-minute mark and the enthralling riff that follows, the song never ceases to build. Just as the lyrical character’s anticipation and terror escalates on his walk to the gallows, so builds the power of the track. By the end of the song, as Bruce Dickinson belts “Yeah! Yeah! Yeah! Hallowed Be Thy Name!” the listener is in full-out headbanging frenzy. With winding, weaving, harmonizing twin solos from Adrian Smith and Dave Murray, and thunderous backing from bestial bassist Steve Harris and drummer Clive Burr, the song is, perhaps, the perfect distillation of the unmatchable Iron Maiden formula.

8. “One,” Metallica

The fourth single from their …And Justice for All album, “One” displays Metallica at the height of their immense powers. The music is dark, the lyrics even darker, and it was simply a stroke of genius for the band, who up to this point had vehemently eschewed making videos, to make “One” the first video they would ever put on MTV. Oh, and what a devastating punch to the gut it was to the uninitiated! Based on a 1939 novel about a soldier maimed in war – his arms, legs, ears, nose, mouth and eyes all gone – nothing intact except for his ability to think and to realize that he is forever confined to the dark isolation of his own tortured thoughts (no one to hear his silent pleas of “kill me… kill me…”) many MTV viewers were horrified. Heavy metal fans, however, were jubilant as they celebrated the dawning of a new era. There was a new sheriff in town on MTV, and its name was Metallica!

7. “Paranoid,” Black Sabbath

If “Iron Man” represents the slow, near dirge-like side of heavy metal, then “Paranoid” is its rapid-fire brother. Centered on Tony Iommi’s menacing, proto-punk riff and Ozzy Osbourne’s banshee vocal, the song established a template from which bands as varied as Metallica and Nirvana would later draw. Geezer Butler’s rumbling bass lines and Bill Ward’s full-throttle drumming were key as well, as both established the hyper-charged rhythmic backdrop against which Iommi and Osbourne could shine (albeit darkly). “It’s just something that came out of me that was totally different,” Iommi later said, of the guitar style he fathered. “It was doomy and the riffs were a bit frightening. It’s a really mystical thing.” Indeed, like a locomotive hurtling into a violent thunderstorm, “Paranoid” remains at once thrilling and frightening.

6. “War Pigs,” Black Sabbath

It’s not an easy task to choose which Sabbath song is the greatest (hence why three of them are clustered together here in the Top 10), but you might call “War Pigs” the band’s best epic. From the lead-footed sludge of the opening minute, to the moment Tony Iommi bursts in with the gut-punching riff to the outstretched coda (named “Luke’s Wall” in honor of roadies Geoff “Luke” Lucas and Spock Wall), “War Pigs” has everything you want in a Sabbath song. Each member was firing on all cylinders on this one. Bill Ward has never been more thunderous, Geezer Butler kicks out a killer groove, Iommi’s blues-metal genius is on full display and Ozzy Osbourne’s sour howl sounds perfectly satanic – even though the lyrics were altered to be about the horrors of war. Becoming a metal standard, it’s been covered numerous times, but no one’s ever matched the brute force of the original.

5. “The Number of the Beast,” Iron Maiden

Evil is an intrinsic part of metal and, like “Black Sabbath,” Iron Maiden’s “The Number of the Beast” takes the listener as close to that evil as they can bear. The song’s legendary scream of anguish after the intro is as real as it gets – legend has it that the moment is a recording of singer Bruce Dickinson’s real reaction to being asked to record yet another take. Meanwhile bassist and lyricist Steve Harris’ narrative was inspired in part by a nightmare he had after seeing the film The Omen and partly by the 1790 poem Tam o’Shanter by Robert Burns, in which the protagonist similarly witnesses all kinds of ghoulish goings-on. Musically the song is uptempo and hypnotic, with the requisite shout-along chorus and a tension-building bridge which is relieved by a classic Dave Murray/Adrian Smith shred vs. blues solo duel.

4. “Iron Man,” Black Sabbath

Tony Iommi grinds out some riffs, Ozzy Osbourne starts humming and says it sounds like an iron bloke walking about. Geezer Butler runs with the line, turns it into a song and a Sabbath classic is born. With the pounding power of Iommi’s riff, the strident vocals and the imagination-teasing storytelling, this was a new kind of rock. It was darker, gloomier, nastier and bolder than Zeppelin and Purple. Black Sabbath weren’t hard rock, Sabbath were metal.

3. “Crazy Train,” Ozzy Osbourne

The pressure was on Ozzy Osbourne in 1980. His crazy antics had led to his departure from Black Sabbath and the launch of, hopefully, a new solo career. Randy Rhoads’ outrageous guitar work, as well as Rhoads’ songwriting collaborations, ensured that so long as Ozzy could come up with decent lyrics and still force fire from his belly, the career would be in good shape. “Crazy Train” was near perfect in concept and execution. All Aboard!

2. “Ace of Spades,” Motörhead

Maybe “Ace of Spades” is technically more hard rock than metal – but it certainly rocks harder and faster than any song known to man (metal or otherwise). From the moment Lemmy hits the gas pedal on the opening bass riff, the song never relents. “Philthy Animal” Taylor nobly powers the drums forward at a frenetic pace and “Fast” Eddie Clarke is more than up to the task of ripping a blazing solo directly after the breakdown. And oh, that breakdown. “You know I’m born to lose/And gambling is for fools/But that’s the way I like it, baby/I don’t want to live forever! – And don’t forget the Joker!” If that doesn’t set your blood boiling, then you simply don’t have a pulse.

1. “Master of Puppets,” Metallica

Metallica were already high on the heavy metal watch list with Kill ’em All and Ride the Lightning, but 1986’s Master of Puppets was the ultimate statement of intent, as much a call to arms for metalheads everywhere as it was a dire warning of the enslaving power of drug abuse. The song’s razor-sharp intro riff sets up the perfect headbanging tempo in the chugging verses, while it’s every teenage metal fan’s sacred rite of passage to scream out “Master! Master!” at the top of their lungs to this song (preferably at a Metallica concert, but at the very least from a car window). The breakdown and harmony line are balanced by a rare James Hetfield solo (with Hetfield revealing a surprisingly bluesy, haunting and emotional lead style), a return to the harmony, then a blazing Kirk Hammett solo. By the end of the song, it’s obvious that metal would never be the same