Halford was born in Sutton Coldfield, but raised on the Beechdale housing estate in Walsall, a town to the northwest of Birmingham in England's West Midlands. His early influences included soul screamers, such as Little Richard, Janis Joplin and Robert Plant.
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Halford was introduced to Judas Priest co-founder Ian Hill by his sister, who was dating Hill at the time. Halford, a manager of a porn cinema, joined the band as singer, bringing with him drummer John Hinch from his previous band, Hiroshima.
In August 1974, the band debuted with the single "Rocka Rolla", before releasing an album of the same name a month later. The next albums were Sad Wings of Destiny (1976); 1977's Sin After Sin; and 1978's Stained Class and Killing Machine (released in America as Hell Bent for Leather). 1979 brought their first live recording with Unleashed in the East.
In 1980, the band released British Steel, then Point of Entry in 1981, featuring the song "Heading Out to the Highway".
The 1982 album Screaming for Vengeance had a song, "You've Got Another Thing Comin'", which garnered strong US radio airplay, and the popular follow-up Defenders of the Faith was released in 1984. Turbo was released in April 1986. In May 1988, Ram It Down was released.
In September 1990, the Painkiller album dropped the 1980s-style synthesizers for almost all of the songs. Along with a change in musical style, the band's look changed as well. Halford emerged with all-new tattoos, including a bent Judas Priest cross on his right arm and ring around his other, as well as a few on his shoulders. He also began shaving his head.
During the tour for Painkiller in August 1991 at a show in Toronto, Halford rode onstage on a large Harley-Davidson motorcycle, dressed in motorcycle leathers, as part of the show. He collided with a half-raised drum riser and fell off the motorcycle, breaking his nose.
After regaining consciousness, Halford returned and performed the whole concert. In the band's Behind the Music episode, he named the accident as one of the events that caused the rift between him and the rest of the band that would eventually force them apart.
After spending nearly 20 years with Judas Priest, Halford announced to the band on 4 July 1991 that he was leaving, and he also sued their label, Sony, for restrictive practices. Halford would leave the band in May 1992.
Fight, 2wo and Halford
Halford first formed the band Fight with Judas Priest drummer Scott Travis, bassist Jack "Jay Jay" Brown and guitarists Brian Tilse and Russ Parrish, recording two albums between 1993 and 1995: War of Words (1993) and, after Parish's departure and his replacement by Mark Chausee, A Small Deadly Space (1995). While the first one was a straightforward tough and solid metal record, the second record had a grungier sound, making it less appealing to fans who had developed a taste for his debut album.
Between the albums, Fight released an EP, Mutations, featuring War of Words studio versions, live cuts and alternate mixes. Immediately before this, Halford had recorded a track called "Light Comes Out of Black" for the 1992 movie Buffy the Vampire Slayer. The song featured music provided by Pantera, although their contribution is uncredited.
After Fight, he collaborated with guitarist John Lowery in an industrial-influenced project called 2wo which was executively produced by Trent Reznor and released on his Nothing Records label.
Halford returned to his metal roots in 2000 with his band Halford and the widely acclaimed album Resurrection (2000), produced by Roy Z. He joined the Metal 2000 tour with Iron Maiden and Queensrÿche to support the album. A live album in 2001 was followed up by Crucible (2002).
Reunion with Judas Priest
Halford often rides a motorcycle onstage.
Halford's reunion with Judas Priest had been speculated about when he was no longer in the line-up, at least since the release of the Resurrection album, which some critics claimed sounded more like Judas Priest than the band's previous album Jugulator (1997). Halford initially ruled it out, then reconsidered, stating in 2002 that "Gut instinct tells me that at some point it will happen".
In July 2003, Halford returned to his former band, and they released Angel of Retribution in 2005. The world tour that accompanied the release marked the band's 30th anniversary. In 2008, Halford recorded Nostradamus with Judas Priest, and appeared with the band on the Metal Masters Tour.
In 2011, Judas Priest embarked upon what was billed as their final world tour as a group, titled the "Epitaph" tour.
Subsequent to the tour's announcement, Halford stated that he would continue to move forward with his solo band.
Despite the "final tour" announcement in 2011, Halford and Judas Priest (minus K. K. Downing, who left the group prior to the Epitaph tour) recorded another album, Redeemer of Souls, which was released in 2014, the album supported by a concert tour.
In 2017, Judas Priest began to work on another studio album with Halford. The album, Firepower, was released March 9, 2018.
Halford has performed as the vocalist for Black Sabbath for three shows. He replaced Ronnie James Dio for two nights in November 1992, when Dio elected not to open a show for Ozzy Osbourne. Halford also filled in for Osbourne in Black Sabbath on 26 August 2004 (one day after Halford's 53rd birthday) at an Ozzfest show in Camden, New Jersey, since Osbourne could not perform due to bronchitis.
In early 2008, Halford expressed a desire in making a black metal album, citing encouragement from former Emperor frontman Ihsahn. He said he'd "love to but it's all about finding the time". He provides his voice to the video game Brütal Legend, released in October 2009, where he voices General Lionwhyte, as well as the leader of the Fire Barons, he heavily influenced the appearance of the latter.
In 2002, Halford had a small role as a sex shop assistant in the film Spun.
In 2006, Halford split with Sanctuary Records and founded Metal God Entertainment in Phoenix, AZ, as a record label to release albums DVDs from his projects.
Halford developed the clothing line Metal God Apparel with plans to develop retail sales through 2010.
Halford had a brief cameo in a recent commercial for Virgin Mobile, appearing as a priest. His line in the commercial is "Let us pray". Judas Priest's 1977 album, "Sin After Sin" contained a song titled "Let Us Prey/Call for the Priest".
In 2013, he did a collaboration with Five Finger Death Punch in their album "The Wrong Side Of Heaven and the Righteous Side of Hell" for the song "Lift Me Up". 
In March 2019, Halford told New Zealand news outlet Stuff that he was working on an autobiography, the idea having been "rattling around in my head forever.” Halford said his principal motivation in writing a book would be “to tell your side of the story from the horse’s mouth, as opposed to something that has been knocked up by somebody else from a bunch of interviews and so forth.” Halford joked that “between my early childhood, adolescent years and the place where I’m at now,” the result would be a trilogy like The Lord of the Rings.