Toxic metals are dangerous environmental pollutants due to their toxicity and strong tendency to concentrate in environment and in food chains. Microorganisms affect the solubility, bioavailability, mobility of heavy metals in soil. Bioremediation techniques (phytoremediation, rhizoremediation, biosorption by biomass and the use of biopolymers) are the most promising technologies for removing these compounds from contaminated soil and wastewater. This contribution reviews basic microbial processes in transforming toxic metal contaminants and promising new biotechnology approaches in remediation of contaminated soils.