King was born in Huddersfield, England[note 1] to an Australian father and an English mother.[4] His father David is a former professional rugby league player who was playing for the Huddersfield Giants at the time of King's birth.[3] His mother is from Dewsbury.[3]
He lived in Huddersfield until aged 7 when he and his family moved to Australia. He lived in Maitland and was educated at All Saints College, Maitland. It was there where he represented NSW Combined Catholic Colleges Rugby League team.
In 2016 and 2017, King played for the Gold Coast Titans' NYC team.[8][9] Max King won the Titans Holden Cup Player Of The Year in 2016 before moving up to first grade in 2017
2017
In round 3 of the 2017 NRL season, King made his NRL debut for the Gold Coast club against Parramatta.[10][11] King won the Titans Rookie Of The Year in 2017
In round 20 of the 2020 NRL season, King played his 50th NRL match, during the match King was placed on report for a hip drop tackle on St. George Illawarra forward Blake Lawrie. Due to the intent shown from King the tackle was referred straight to judiciary. King was later suspended for three matches by the judiciary costing himself a chance of playing in the 2020 NRL Grand Final. The tackle was described as being ugly and premeditated.[13]
After playing off the interchange bench in the opening seven games of the 2022 season, King made his Canterbury run-on debut in their round 8 match against the West Tigers at Leichhardt Oval. Under interim coach Mick Potter he has consolidated himself in the starting 13, both in the back row and at prop. King played a total of 24 matches for Canterbury in the 2022 NRL season as the club finished 12th on the table.[15]
2023
King played a total of 23 games for Canterbury in the 2023 NRL season as the club finished 15th on the table.[16]
2024
King played 21 games for Canterbury in the 2024 NRL season as the club qualified for the finals finishing 6th on the table. King played in their elimination finals loss against Manly.[17]