He is best known for his role as Ian Gallagher in the Channel 4 television series Shameless. He first appeared in the role in 2004 and was one of the original characters. In April 2010 Gerard announced that he was quitting the role to pursue other projects.
Gerard starred in the film The Mark of Cain, for Film4 Productions, based on British soldiers' abuse of Iraqi prisoners. It premiered at the International Film Festival in Rotterdam in February 2007.
He has also starred int he short films Grandad and The 10th Man and has appeared in a number of TV shows such as The Commander starring Amanda Burton.
In 2007 he also featured as a voice over for BBC's GCSE Bitesize Revision.
Gerard was cast in the second series of the BBC 1 daytime show Moving On. The episode Trust, directed by Illy, tells the story of Gerard's character Jack, who is caught trying to burgle the house of elderly ex-boxer Eddie, played by Roy Marsden.
He has also made several appearances in The Accrington Pals, a play by Peter Whelan, portrying the character Ralph, a young volunteer officer during the First World War. The extent of his stage career has been seemingly limited to his local area of Manchester.