Kevin Patrick Shields was born on 21 May 1963 in Jamaica Hospital in Queens, New York City, United States. He is the eldest of five siblings born to Irish parents; his mother was a nurse and his father was an executive in the food industry. Shields' parents had emigrated to the United States from Ireland in the 1950s, when the couple were teenagers. Shields attended Christ the King, a Roman Catholic primary school which he described as "a really horrible school run by psychopathic nuns".

Shields' guitar sound has been cited as one of the most recognisable aspects of My Bloody Valentine's music. His sound uses "texture more than technique to create vivid soundscapes". He has been listed at number 95 and 2  on Rolling Stone's and Spin's 100 Greatest Guitarists of All Time list. During the late 1980s, Shields began customising the tremolo systems for his Fender Jaguars and Jazzmaster guitars; he extended the tremolo arm and loosened it considerably, to allow him to manipulate the arm while strumming chords, which resulted in significant pitch bending. Shields used a number of alternate and open tunings that together with his tremolo manipulation, according to Rolling Stone's Michael Azerrad, achieved "a strange warping effect that makes the music wander in and out of focus".  Among Shields' notable effects is digital reverse reverb, sourced from a Yamaha SPX90 effects unit. Together with the tremolo manipulation and distortion, he created a technique known as "glide guitar". Shields effects rig, which is composed largely of distortion, graphic equalisers and tone controls, consists of at least 30 effects pedals. His rig is connected to a large number of amplifiers which are often set to maximum volume to increase sustain. During live performances with My Bloody Valentine - particularly during the closing "You Made Me Realise" - Shields creates a blend of noise and excessive feedback, known as "the holocaust", which has often lasted for half an hour and often reached 130db. "It was so loud it was like sensory deprivation," he remarked. "We just liked the fact that we could see a change in the audience at a certain point."  Shields' sound and performance have been regarded as influential, with musicians including Billy Corgan and J Mascis citing him as an influence.  "Kevin Shields achieved something on Loveless that only the great guitarists achieve: he achieved a wholeness and a unity," observed Living Colour's Vernon Reid. "He created his own sound."

What was special about the guitar sound?
has been cited as one of the most recognisable aspects of My Bloody Valentine's music.