The first and last word in metal. I first heard Iron Man at 8 years of age and have been hooked ever since. Never heard a Sabbath tune I didn't like. Ozzy's ability to come up with great riffs (yes, it was Ozzy that came up with them), Iommi's phenominal playing, Geezer's awesome bass and lyric writing, Ward's powerful drumming all combine to create the sound that gave rise to the genre of Metal and all it's subgenres.
The second most influential artist of my "Big Three" that started me on this 40 year voyage through Rock and Metal. While many will argue that Zep isn't a Metal band,(I say they are), they nonetheless have generated scores of songs that have heavily influenced Metal and all of Rock in general. Page's intricate guitar passages, Plant's vocal ability, the bass work of John Paul Jones, and the brilliant drumming of Bonham forged some of the greatest music ever.
The third major influence in the formation of my musical taste. Blackmore is as good a guitarist as any. He has come up with some of the most memorable riffs in Metal. Gillan has one of the best vocal ranges of any singer (just listen to Child In Time if you don't believe me). The great keyboard work by Jon Lord, and one the the best ever rythym sections in Glover and Pace helped to drive this band to the top of list.
The best Progressive band ever. While their early work with Syd Barrett was quirky, they still had some gems in tracks like Arnold Lane and Interstellar Overdrive. Floyd can play almost any type of music from Metal (The Nile Song, Ibizia Bar) to progressive (Shine On You Crazy Diamond, Great Gig In The Sky). In 1980 they created a masterpiece with The Wall.
Tyler's unique raspy voice, combined with the powerful twin guitars of Perry and Whitford, and grounded by the fine rythym section of Hamilton and Kramer, powered Aerosmith to the top of the charts. They produced some of the finest hard rocking tunes ever. Such songs as Train Kept A Rollin', Sweet Emotion, Last Child, and the legendary Dream On are classic tracks that have had a major impact on the Rock world.