McMichael was born on February 24, 1952 in Hot Springs, Arkansas and graduated from Hot Springs High School, which includes Bill Clinton amongst its graduates.
McMichael enlisted in the United States Marine Corps on 27 August 1970, and attended recruit training at San Diego, California.
In June 1971, after completing Infantry Training School and Basic Infantry Training at Camp Pendleton, California, McMichael was assigned to Marine Barracks, Pearl Harbor, Hawaii. In May 1973, he was transferred to 2nd Battalion 5th Marines at Camp Pendleton. In December 1973, he returned to Marine Corps Recruit Depot San Diego to serve as a drill instructor, series Gunnery Sergeant, and battalion drill master. In December 1975, he was transferred to 1st Battalion, 7th Marines, at Camp Pendleton.
In January 1978, McMichael transferred to the 3rd Marine Division, where he served as a shore party chief with the 3rd Division Support Group. In January 1979, he received orders to Marine Security Guard School and, upon completion of the training, was assigned to the American embassy in Copenhagen, Denmark. In May 1981, he returned to Quantico, Virginia to serve as an instructor for the Marine Security Guard School.
In May 1983, McMichael was assigned to the University of Minnesota where he served as the Assistant Marine Officer Instructor for the NROTC Program. In December 1984, after completing the Staff Noncommissioned Officers Academy Advanced Course, he was transferred to Okinawa, Japan to serve as the First Sergeant of Company C, 3rd Reconnaissance Battalion. In January 1986, he was ordered to Marine Barracks, Roosevelt Roads in Puerto Rico, to serve as the barracks's first sergeant.
McMichael served as the director of the Staff Noncommissioned Officers Academy at Marine Corps Air Station El Toro, California from May 1989 to May 1991, after having served as the school's deputy director since August 1988. In May 1991, McMichael was transferred to Quantico again, where he served as the Sergeant Major of Officer Candidates School.
In June 1994, he returned to Okinawa, Japan where he served as the Sergeant Major of the 31st Marine Expeditionary Unit until July 1995 when he was reassigned as the Sergeant Major of the 1st Marine Aircraft Wing. From January 1997 to June 1999, he served as the Sergeant Major for Manpower and Reserve Affairs Division, Headquarters Marine Corps.
On 1 July 1999, McMichael assumed his post as the 14th Sergeant Major of the Marine Corps, becoming the first African-American to hold the post. His tenure as the Sergeant Major of the Marine Corps saw the establishment of the Marine Corps Martial Arts Program and the commencement of the Global War on Terrorism.
In June 2003, deferring his planned retirement, McMichael assumed a newly created post as the Senior Non-Commissioned Officer for Allied Command Operations, becoming the senior enlisted advisor to General James L. Jones, Supreme Allied Commander, Europe; and Commander, United States European Command, which was technically a demotion from his previous rank and position. He and General Jones previously served together while the latter was the 32nd Commandant of the Marine Corps. McMichael served in this role from June 2003 until July 17, 2006, when he was succeeded by Army Command Sergeant Major Michael Bartelle. He retired from the Marine Corps shortly after with his highest appointed rank of Sergeant Major of the Marine Corps.
McMichael sits on the steering committee of the National Symposium for the Needs of Young Veterans, hosted by AMVETS.
In 2003, the Boys & Girls Clubs of America citing that "the Sergeant Major [had] come a long way from segregated Hot Springs, where the Club was the only colorblind place to play," named McMichael to its "Alumni Hall of Fame." McMichael commented, "The Club gave me those things I use today in the Marine Corps . . . You made a difference in one child’s life." McMichael credits the Club, which he joined at age 9, with giving him a vision of what the world should and could be.
In 2008, McMichael's memoirs were published under the title LEADERSHIP: Achieving Life-Changing Success From Within.8 service stripes.