Singer-songwriter Ryan O'Shaughnessy is among the lineup, following his reinstatement into the competition last weekend after his contract with Ireland's The Voice was cancelled.
Basketball stunt act Face Team and 16-year-old singer Hope Murphy will also appear.
Laser harp musician Grieg Stewart, wheelchair dancers Strictly Wheels and Cyr wheel performer Billy George will also take to the stage.
The lineup is completed by Dalek impersonator Martyn Crofts, comedian Callum Oakley and synchronised swimming group Aquabatique.
Ashleigh & Pudsey, Jonathan & Charlotte and the Loveable Rogues will be among Saturday's finalists.
The Britain's Got Talent semi-finals conclude tomorrow (May 10) at 7.30pm on ITV1.
Photo gallery: Britain's Got Talent's fourth semi-final:
Copyright: Rex Features Ken Mckay/Thames