This review from 2017 outlines the role of this important essential metal in proper immune function, regulation of blood sugar and cellular energy, reproduction, digestion, bone growth, blood coagulation, and hemostasis and defense against reactive oxygen species. The beneficial effects of manganese are due to the incorporation of the metal into metalloproteins.
Aschner M, Erikson K. Manganese. Adv Nutr. 2017 May 15;8(3):520-521. doi: 10.3945/an.117.015305. PMID: 28507016; PMCID: PMC5421128.