George was born on the island of Corfu in northwest Greece in 1940. There, he completed his secondary education before attending the University of Athens. He graduated from the University of Athens, having obtained a degree in Theology in 1962, and then another in Classical Literature in 1967 after he had completed military service from 1963 to 1965.
After receiving his degree in 1967, George became Research Assistant at the Department of Patrology at the university. In 1969, he took up residence in Western Germany and began post-graduate studies. During this time he attended schools in Bonn and Cologne and also conducted studies and archival research in England. In 1971, he was ordained into the clergy and received a Doctor of Theology degree from the University of Athens and a Doctor of Philosophy - History degree from the University of Cologne.
In 1984, Dr. Metallinos became a Professor at the School of Theology of the University of Athens, where he taught History of Spirituality during the Post-Byzantine Period, History and Theology of Worship, and Byzantine History. In 2004, he was appointed Dean of the School of Theology, a position in which he served until 2007 when he became professor emeritus.
Fr. Metallinos has been a prolific writer, with more than 40 books in Greek. Among these, with their titles in translation, are:
- Protopresbyter John S. Romanides, ISBN 960-527-274-1, Armos, Athens, Greece, 2003
- For our Europe with Love, ISBN 960-328-219-7, Akritas, Athens, Greece, 2003
- Essays of Orthodox Witness, ISBN 960-85130-6-5, Athos, Athens, Greece, 2002
- Sources of Ecclesial History, ISBN 960-7102-43-6, Armos, Athens, Greece, 2001
- Church and State in the Orthodox Tradition, ISBN 960-527-165-6, Armos, Athens, Greece, 2000
- Politics and Theology, ISBN 960-7297-04-0, Tertios, Athens, Greece, 2000
- Orthodoxy and Hellenicity, ISBN 960-7956-21-4, Parousia, Athens, Greece, 1999
- The Theological Witness of Ecclesial Worship, ISBN 960-7102-70-3, Armos, Athens, Greece, 1996
- Tradition and Alienation, ISBN 960-7217-04-7, Domos, Athens, Greece, 1961
And published in English:
- I confess One Baptism, ISBN 978-960-85542-0-7, St. Pauls Monastery, Holy Mountain, Greece, 1994