Porter was born Nov. 15, 1999 in Columbia, Missouri. Porter has seven siblings. His mother, Lisa played college basketball at Iowa while his father, Michael Sr., played collegiately at New Orleans. Like his older brother, Michael, he began his high school career playing for the Father Tolton Regional Catholic High School in Columbia. As a freshman, he averaged 11.8 points and 7.8 rebounds per game, and as a sophomore, he won the Missouri Class 3 State Championship. After that, he attended Nathan Hale High School in Washington state, where they went a perfect 29-0 in his time there and won the Washington Class 3A State Championship. During that time, Porter averaged 14.3 points and 13.6 rebounds. After high school, Porter played at Missouri as a freshman before missing his sophomore season due to injury and then declaring for the 2019 NBA Draft. As a freshman, he averaged 9.9 points, 6.8 rebounds, 2.2 assists and 1.7 blocks. As a result, he was named SEC Sixth-Man of the Year.