What form is mostly widely used for a blues song?

The most widely used form for a blues song is the 12-bar blues structure. This format typically consists of three chords, following a specific chord progression over 12 measures, often with a pattern of four bars for each of the three lines of lyrics. The structure allows for expressive storytelling and improvisation, making it a foundational element in Blues Music. Variations like the 8-bar and 16-bar blues also exist, but the 12-bar format remains the most iconic.