Chief Sully began his fire service career in 1993 as an explorer and eventual volunteer firefighter with the Bennett Valley Fire Department through 2005. He was hired by CAL FIRE in 2000 when he accepted a Firefighter position in the Sonoma Lake Napa Unit (LNU) at the Occidental Station. Matt has spent the majority of his career in LNU where he was worked as a Fire Fighter II in 2004, Fire Apparatus Engineer in a Limited Term capacity in 2003, and permanent in 2006, Fire Captain in 2009, and a Limited Term Battalion Chief in 2018. The assignments he held included both Schedule A and Schedule B programs as well as the Training Bureau. In September 2018, Matt accepted a permanent Battalion Chief position in the Santa Clara Unit overseeing the Training Bureau.

In March 2020, he accepted a promotion to the LNU Administrative Assistant Chief position. In October 2021, Matt accepted the position of Deputy Chief of State and Federal Programs in Sacramento. In April 2022, Matt accepted the Staff Chief of Cooperative Fire Protection overseeing the Local Government Program, State and Federal Programs, Administrative Support, and the Camps and Crews Program. In January 2023, he accepted the Assistant Deputy Director of Cooperative Fire Protection overseeing the Local Government Program, State, Federal, and International Programs, as well as the Camps and Crews Program.

Chief Sully has been a member of CAL FIRE Incident Command Team 4 and Incident Management Team 5 in roles as the Hired Equipment Technical Specialist and Operations Branch Director. In addition, he has served on the Napa County Interagency Hazardous Materials Team and has been a member of the statewide Hired Equipment Committee, the Personal Protective Equipment (PPE) Workgroup, and the 10000 Hired Equipment Handbook Work Group. Matt is a certified instructor with the California Specialized Training Institute/State Fire Training and has completed his Fire Officer certification through State Fire Training. He is currently serving as the lead of the CFMA 2024 renewal working group and sits on the CFAA Committee representing CAL FIRE.