After attempting to learn to play right-handed, Iommi strung his guitars with extra-light strings (using banjo strings, which were a lighter gauge than even the lightest guitar-strings of the time) and wore plastic covers over the two damaged fingers. He fashioned the latter himself, by melting plastic liquid-soap bottles into a ball and then using a soldering iron to make holes into this ball, putting his fingers in while the plastic was still soft enough to be shaped. He then trimmed and sanded away the excess plastic to leave himself with two thimbles, which he then covered with leather, to provide better grip on the strings. Subsequent tips have been custom-made.
Iommi had played in several blues/rock bands, the earliest of which was The Rockin' Chevrolets between 1964 and 1965. The band had regular bookings and when they were offered work in Germany, Iommi decided to leave his factory job to take up the opportunity. Between 1966 and 1967 Iommi played in a band named The Rest. This was the first time Iommi played with old school friend and future Black Sabbath drummer Bill Ward.
From January 1968 till July 1968, Iommi was guitarist in Mythology, with Ward joining a month later in mid-February. In May 1968, police raided the group's practice flat and found cannabis resin, which resulted in a £15 fine and a two-year conditional discharge for Iommi, Ward, Smith and Marshall. Mythology split up after a gig in Silloth on 13 July 1968.
In August 1968, at the same time as the breakup of Mythology, a band called Rare Breed also broke up. Rare Breed vocalist John "Ozzy" Osbourne and rhythm guitarist Terry "Geezer" Butler joined with Iommi and Ward from Mythology and also slide guitarist Jimmy Phillips and saxophonist Alan "Aker" Clarke. The six-piece band, now with Butler as bassist, were named the Polka Tulk Blues Company. After just two gigs (the last of which was at the Banklands Youth Club in Workington), Phillips and Clarke were dismissed from the band, which soon after shortened its name to Polka Tulk.
Iommi, Butler, Ward and Osbourne renamed their band Earth in September 1968. They carried on under this moniker until December 1968 when Iommi briefly departed to play in Jethro Tull. However after only one performance (an appearance on "The Rolling Stones Rock & Roll Circus" in which the band mimed "A Song For Jeffrey", whilst Ian Anderson sang live), Iommi was back with Earth once more.
Tony Iommi on his brief working relationship with Jethro Tull vocalist Ian Anderson:
'I learned quite a lot from him, I must say. I learned that you have got to work at it. You have to rehearse. When I came back and I got the band (Earth) back together, I made sure that everybody was up early in the morning and rehearsing. I used to go and pick them up. I was the only one at the time that could drive. I used to have to drive the bloody van and get them up at quarter to nine every morning; which was, believe me, early for us then. I said to them, "This is how we have got to do it because this is how Jethro Tull did it." They had a schedule and they knew that they were going to work from this time till that time. I tried that with our band and we got into doing it. It worked. Instead of just strolling in at any hour, it made it more like we were saying, "Let’s do it!"
In August 1969, following the confusion with another group named Earth (who had minor success in England), the group renamed themselves Black Sabbath. His aforementioned factory accident affected the Black Sabbath sound later on, as Iommi detuned his guitar from E to C# (3 half-steps down), in order to ease the tension on his fingers. As a result, Sabbath were among the first bands to detune and resulted in the technique being a mainstay of heavy metal music. The first two Black Sabbath albums are actually in E tuning, however, as Iommi didn't start tuning down to C# until 1971's Master of Reality. Black Sabbath bassist Geezer Butler also tuned his instrument down to match Iommi's. Iommi combined blues-like guitar solos and dark, minor-key riffing with a revolutionary high-gain, heavily distorted tone with his use of a modified treble-boosting effect-pedal and a Gibson SG, as well as plugging his guitar into his amp's bass input.
Rob Halford, vocalist for Judas Priest, when filling in for Ozzy Osbourne during an August 2004 concert in Philadelphia, introduced Tony Iommi to the audience as "The man who invented the heavy metal riff".
By the mid 1970s, incessant drug usage, managerial problems and constant touring had taken its toll on the band, and Ozzy Osbourne was fired in 1979 by Iommi. Osbourne was replaced with Ronnie James Dio, the vocalist for Rainbow (a band formed by former Deep Purple guitarist Ritchie Blackmore). With Dio, Black Sabbath produced Heaven and Hell, prior to replacing Bill Ward with Vinny Appice. With Iommi and Geezer Butler the only original members, this line-up produced Mob Rules. During the '80s and '90s Iommi rebuilt the band with many lineup changes with vocalists including Ian Gillan (formerly of Deep Purple), Glenn Hughes, Tony Martin and Ray Gillen. After Ian Gillan departed the band in 1984, Iommi recorded his first solo album, entitled Seventh Star. The album featured Glenn Hughes (formerly of Deep Purple) on vocals, but due to label pressures, it was billed as a release by "Black Sabbath featuring Tony Iommi."
In 1992, Iommi appeared at the Freddie Mercury Tribute Concert, playing four songs with the remaining members of Queen and other guest artists. Also, in the following year Iommi teamed up with fellow Black Country band Diamond Head and co-wrote the song Starcrossed (Lovers in the Night) for their 1993 Death and Progress album. At Ozzy's 'farewell' concert at Costa Mesa in 1992, Ronnie James Dio refused to perform and abruptly left the band. As a result, Rob Halford (vocalist for Judas Priest) was recruited to perform as the vocalist for two gigs (Halford also sang at one of the dates on the 2004 Ozzfest tour, when Ozzy couldn't perform due to bronchitis). The show concluded with Ozzy bringing out the other members of the original Black Sabbath line-up (following the end of Osbourne's solo set) for a 4-song reunion.
Black Sabbath went on to record 2 further albums with another of their previous vocalists Tony Martin before the original line-up reunited as a touring band in 1997 (although Bill Ward was not present for the first two reunion tours, the second being due to a heart attack. Ward was replaced by Vinny Appice.)
In 2000, Iommi finally released his first legitimate solo album, titled Iommi. The album featured several guest vocalists that included Ian Astbury, Henry Rollins, Serj Tankian, Dave Grohl, Billy Corgan, Phil Anselmo, Peter Steele and Ozzy Osbourne. In late 2004, Iommi's second solo album was released, entitled The 1996 DEP Sessions. This album was originally recorded in 1996, but was never officially released. However, a copy with a drum track by Dave Holland was available as a bootleg called Eighth Star. Glenn Hughes performed vocals on the album, and he furthered his collaboration with Hughes with the release of his third solo album, Fused. Released on 12 July 2005, John Mellencamp drummer Kenny Aronoff completed the trio on the album.
Iommi has signed with Mike Fleiss' movie production company Next Films to score a series of horror films entitled Black Sabbath.
In October 2006 it was reported that Iommi would tour with Bill Ward, Geezer Butler and Ronnie James Dio again, but under the moniker Heaven and Hell. Later it was announced that Ward had decided not to participate and Vinny Appice was hired as his replacement. Rhino Records released "The Dio Years" (under the 'Black Sabbath' moniker) album on 3 April 2007. The album showcased older tracks with Dio and also included three brand new songs recorded with Dio and Vinny Appice.
The band started an American tour in April 2007 with Megadeth and Down as opening acts. The tour finished in November in England with the prospect of an album to follow in 2008. During this period the band's show at the New York Radio City Music Hall was released as both a DVD and CD with a vinyl release expected in the UK in 2008. During the summer of 2008, the band embarked on the Metal Masters Tour along with Judas Priest, Motörhead and Testament. The band's first studio album, The Devil You Know, was released on April 28, 2009.
In November 2008, Iommi had a star revealed on the Birmingham Walk of Stars.
Currently, Iommi is being sued by bandmate Ozzy Osbourne over ownership of the "Black Sabbath" name.
In a statement on his official website Osbourne has said:
"It is with great regret that I had to resort to legal action against my long term partner, Tony Iommi, but after three years of trying to resolve this issue amicably, I feel I have no other recourse. As of the mid-1990's, after constant and numerous changes in band members, the brand of 'Black Sabbath' was literally in the toilet and Tony Iommi (touring under the name Black Sabbath) was reduced to performing in clubs. Since 1997 when Geezer, Bill and myself rejoined the band, Black Sabbath has returned to its former glory as we headlined sold-out arenas and amphitheatres playing to upwards of 50,000 people at each show around the world. We worked collectively to restore credibility and bring dignity back to the name 'Black Sabbath' which lead to the band being inducted into the UK and US Rock & Roll Hall of Fames in 2005 and 2006, respectively. Throughout the last 12 years, it was my management representatives who oversaw the marketing and quality control of the 'Black Sabbath' brand through OZZFEST, touring, merchandising and album reissues. The name 'Black Sabbath' now has a worldwide prestige and merchandising value that it would not have had by continuing on the road it was on prior to the 1997 reunion tour. Tony, I am so sorry it's had to get to this point by me having to take this action against you. I don't have the right to speak for Geezer and Bill, but I feel that morally and ethically the trademark should be owned by the four of us equally. I hope that by me taking this first step that it will ultimately end up that way. We've all worked too hard and long in our careers to allow you to sell merchandise that features all our faces, old Black Sabbath album covers and band logos, and then you tell us that you own the copyright. We're all in our 60's now. The Black Sabbath legacy should live on long after we have all gone. Please do the right thing."
A Manhattan federal judge ruled, in February 2010, that Osbourne can proceed with the suit but urged both sides to consider resuming mediation.