Shield was first taught music by his father, but after both he and his mother died while Shield was still a child, he was apprenticed to a ship-builder in South Shields, continuing to study with Charles Avison in Newcastle upon Tyne.
Shield became a noted violinist in Newcastle's subscription concerts before moving to Scarborough to lead a theatre orchestra. In 1772 he was appointed by Felice de Giardini to play violin in the opera at Covent Garden (now the Royal Opera House), and from 1773 he was principal violist there.
Shield also worked as a composer for Covent Garden, and in that capacity he met Joseph Haydn. In 1817 he was appointed Master of the King's Musick.
Shield's works include a large number of operas and other stage works, including one on Robin Hood, as well as instrumental music.
There has been some suggestion that a melody in the overture to Shield's opera Rosina is the source of the tune to Robert Burns's "Auld Lang Syne", although this is contested, with the general belief being that both Shield and Burns took the tune from an old folk song.