Born in Wriezen, Müntner completed an apprenticeship as a saddler and travelled extensively in his journeyman years, before settling in Berlin in 1894.
In the role, he focused on supporting the relatives of members who had been called up to fight in World War I, and also served on the city's Nutrition Committee.
He advocated compulsory arbitration in disputes and a national eight-hour working day, and argued against resistance to the Occupation of the Ruhr.
He immediately organised an international congress of energy workers, to campaign against privatisation, but thereafter struggled to achieve much in the role, as the federation's finances worsened.
He recovered sufficiently to become the auditor of the ADGB in 1931, but retired from all his trade union posts in October 1932.