Glaciers cover about 10% of the Earth’s land area but are rapidly retreating due to climate change. Currently, we lack a holistic understanding of the ecological processes and metabolic strategies that enable initial ecosystem development in glacier foreland ecosystems. Here, we reveal that diverse energy sources sustain microbial life in Swiss and Antarctic glacier foreland soils. We applied cutting-edge metagenomic, biogeochemical, and culture-based investigations to profile composition, capabilities, and activities of the respective microbiomes from soil samples along two retreating glacier foreland transects in Switzerland and the Antarctic, which also include depth profile from top-soil to 50 cm below the surface. We reconstructed 761 medium- to high-quality metagenomic assembled genomes spanning 22 phyla. Most microorganisms present were metabolically flexible aerobes that can use both organic and inorganic energy sources. Particularly abundant were bacteria that consume atmospheric hydrogen via group 1l [NiFe]-hydrogenases to support respiration and sometimes carbon fixation. Also present were sulfur-, carbon monoxide-, and methane-oxidising bacteria, ammonia-oxidising archaea, and phototrophic Actinobacteriota, Gemmatimonadota, and Cyanobacteria. The key metabolic groups in these soils showed distinct abundance patterns with soil age and depth. In situ and ex situ experiments showed that the soil microbial communities rapidly consumed atmospheric hydrogen, and less rapidly carbon monoxide and methane, with consumption rates of all three gases increasing with soil age. Together, these findings suggest that primary succession in glacial foreland soils is driven by self-sufficient, metabolically flexible chemotrophs. These habitat generalists are crucial in shaping the initial stages of ecosystem development by creating a more hospitable soil environment for subsequent colonisation to happen.