Lockett studied at Longcroft School in Beverley. He had spent the majority of his career as a machine gunner, when, in 1996, he joined the 1st Battalion of the Worcestershire and Sherwood Foresters Regiment in Tidworth Camp. At this time he held many qualifications, such as the Jungle Warfare Instructor and Military Tracking Instructor.

While fighting in Afghanistan in September 2007, Lockett, then a corporal, and the rest of his unit, were commanded to penetrate enemy lines, and ruin their posts. The Soldiers dubbed the mission 'Operation Certain Death', but carried it out nonetheless. However, they were ambushed by Taliban troops. The ambush caused the death of Private Johan Botha and Sergeant Craig Brelsford, as well as inflicting injuries on four other Soldiers. Michael led the remaining Soldiers in an attempt to retrieve the bodies, and rescue the four injured Soldiers. For his "leadership, command, control and supreme courage", Lockett was awarded the Military Cross on 7 March 2008, which he later received from Queen Elizabeth II.

At the time of his death on 21 September 2009, Lockett was working with the Afghan National Army, at Patrol Base Sandford. He had volunteered to stay at the base because new Soldiers were due to arrive, and he wanted to ensure they knew as much about the local area as possible. He was investigating an improvised explosive device, when it detonated, killing him, and injuring two nearby Soldiers. As well as being the 217th British soldier to die in Afghanistan since October 2001, he is the first soldier who has been awarded the Military Cross to later die there. Lockett was the first MC recipient to be killed in action in living memory.