Plays an important role in homologous strand exchange, a key step in DNA repair through homologous recombination (HR). Binds to single-stranded DNA in an ATP-dependent manner to form nucleoprotein filaments which are essential for the homology search and strand exchange. Catalyzes the recognition of homology and strand exchange between homologous DNA partners to form a joint molecule between a processed DNA break and the repair template. Recruited to resolve stalled replication forks during replication stress. Also involved in interstrand cross-link repair. Forms linear homooligomers, giving rise to a RAD51 nucleoprotein filament, which is essential for strand-pairing reactions during DNA recombination. Accumulated at sites of DNA damage. Recruited to stalled replication forks during replication stress. Belongs to the RecA family. RAD51 subfamily.