His debut role as the child character Otter, in the Academy-Award-winning 1990 film Dances with Wolves, also earned him national notice at thirteen years old. By the age of seventeen, Spears had acted in both TV and film with other actors, including Kevin Costner, Jimmy Smits and Kim Delaney.

He worked with his late father, Patrick Spears, and his brother Eddie on COUP's (Intertribal Council on Utility Policy) Native Energy and Native Wind as part of the Inter-Tribal Group, whose goal is to encourage creation of "natural" sustainable Energy sources. Formed in 1994, COUP provides a forum for utility issues discussion from regulatory and economic perspectives.

Michael Spears was born in Chamberlain, South Dakota near the Lower Brulé Indian Reservation to Native American parents and lived there until he was in fifth grade. After that, his family moved to Pierre, South Dakota. Later, his family moved to Aberdeen, South Dakota where he grew up and graduated Simmons Middle School then Aberdeen Central High School, graduating in 1995.

Spears is an accomplished hand drum player and singer, often performing at Native American powwows and in non-tribal venues (he was the opening act for Rita Coolidge and Friends at her 2005 concert in Great Falls, Montana). Michael often travels to deliver speeches, concentrating on inspirational and educational topics including sustainable Energy, and mentors youth in South Dakota.

He has hosted and co-hosted the American Indian Film Institute Awards, the latest being the 38th Annual American Indian Film Institute Awards in 2013.

In 2014 and 2015, Spears played a recurrent role as Savanukah, a member of the 1777 Cherokee Delegation, in Colonial Williamsburg's open-air stage production of The Beloved Women of Chota: War Women of the Cherokee.