Unable to support his family in Saint-Étienne, he relocated to Lyon, where André became an apprentice in a button factory, but also received drawing lessons.

His work attracted the attention of a local artist named Bergeon, who helped him gain admission to the Academy of Lyon.

In 1779, aged only eighteen, he married Marie-Catherine, née Lejeune., After the factory owner and his wife had died, Galle became the company's sole proprietor.

This prompted the Committee of Public Safety to commission a medal of Hercules and the Hydra; symbolizing the French people destroying the Monarchy.

Later, he would produce a series of medals celebrating the French campaign in Egypt and Syria and, in collaboration with Romain-Vincent Jeuffroy, one for the occasion of Napoleon's coronation as Emperor.