[1] Schmetz became mayor of Neutral Moresnet on 20 June 1885, succeeding Oskar Anton Bilharz to become the territory's fifth mayor.
As mayor, Bilharz served as the territory's head of state, alongside two commissioners, one each from the Kingdom of Prussia and Belgium.
During his term, Germany invaded Belgium on 4 August 1914, initially leaving Neutral Moresnet as "an oasis in a desert of destruction".
As a result of the occupation, Schmetz was removed from his post on 15 March 1915 and Germany appointed Wilhelm Kyll to succeed him.
With a term of nearly 30 years, Schmetz was Neutral Moresnet's second-longest-serving mayor, having served more than a quarter of the territory's existence.