Bacteria-produced melanins have a unique molecular structure and electrochemical properties, which have attracted more attentions in the field of bioelectrochemistry. Firstly, melanin is similar to humus in structure and has the properties of amorphous semiconductor and redox. There are four main types of melanins, including eumelanin, pheomelanin, DHN melanin and pyomelanin, which are divided based on their different synthesis pathways and biochemistry properties. Among them, pyomelanin is mainly produced by bacterial intracellular phenylalanine and tyrosine metabolism. Secondly, bacteria-produced melanins have unique biological functions, which can enhance the survival efficiency by enhancing the pathogenic toxicity of cells, and inhibit marine biofouling by reducing the attachment and deformation of mussel larvae. Lastly, melanins has the electrochemical properties, which influence the corrosion process and electron transfer theory of microbiologically influenced corrosion. Since melanin has redox cycling properties, it is used as an electron donor and acceptor, as well as an electron mediator. The purpose of this review is to elaborate the principle and mechanism of bacterial melanin as an extracellular electron transport particle, and to provide theoretical support and reference for the application of melanin-producing bacteria in the field of microbial corrosion and microbial fuel cells.