He completed his studies in 1950 with a dissertation on the subject of "Elektrochemische Messungen an ungereizten Pflanzenzellen" (Electro-chemical measurements of unstimulated plant cells).
He received his doctorate in 1952 from the University of California, Berkeley, having worked under the direction of the pioneering plant biochemist, Melvin Calvin.
After completing his training at the University of Göttingen, he qualified to become a professor with an investigation about "Veränderung der Blattproteine bei photoperiodischer Induktion"[5] (Changes of leaf proteins by photo-periodic induction).
In addition to the standard academic program, he also organised adult education courses in Baden-Württemberg as of 1981 on ecology and its biological basis, which were attended by more than 6,000 people.
Together with Hans Karl Filbinger, Günter Rohrmoser, Heinz Karst and Erich Baumann, Metzner founded the Weikersheim Think Tank in 1979, and he remained a director until 1995.