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During World War II, Metzger had a close relationship with the President of Finland Risto Ryti and the Minister of Education of Finland, Reverent Antti Kukkonen, who served in the two governments of the Prime Minister of Finland Jukka Rangell.
- "Kolmannen valtakunnan edustajana talvisodan Suomessa" ("As a Representative of the Third Reich in the Winter War Period Finland"). Otava, 1984.
- "Poliittiset aseveljet. Kolmannen valtakunnan edustajana jatkosodan Suomessa 1941–1944" ("Political Brothers-in-Arms. As a Representative of the Third Reich in the Winter War Period Finland, 1941-1944"). Otava, 1986.