Growing up in New Zealand – far from the centres of operatic traditions – McIntyre developed a style uncluttered by centuries of operatic formulae. Initially trained as a school teacher, McIntyre travelled to London in 1958 and studied at the Guildhall School of Music. In 1959 he made his debut with the Welsh National Opera and shortly afterwards joined Sadler's Wells as a soloist. There he met conductor John Matheson, who pointed him in the direction of Wagnerian Opera.

In 1967 he made his Covent Garden debut as Pizarro in Fidelio, starting an association with the Royal Opera House that continues to this day. His roles there have included Kurwenal in Tristan und Isolde, Telramund in Lohengrin, Scarpia in Tosca, Nick Shadow in The Rake's Progress and Kasper in Der Freischütz. He continued to sing at Bayreuth until 1990, finishing with 150 performances to his credit, and gaining immortality as Wotan in Bayreuth's unforgettable centenary Ring Cycle in 1976.

Throughout his career, McIntyre made frequent guest appearances at all the major opera houses of the world. His last New Zealand appearance was in the 2006 International Arts Festival opera, Parsifal. He received a knighthood in 1992 and lives in the United Kingdom.