Jacob Elry Metzger was born on July 30, 1882, in Blair County, Pennsylvania. He graduated from Pennsylvania State College in 1911 and came to the Maryland Agricultural College in 1914. He organized the Department of Agricultural Education and the Maryland Agricultural College's first summer school. The original purpose of the summer session, according to Metzger, was so that "field plots, laboratories, shops, libraries, livestock, orchards, instruction and other facilities used by the regular students of the college might be available to those who for any reason find it more convenient to attend during summer months." The first Summer School, held in 1914, hosted thirty-five courses; the number increased to forty-eight in 1915 (to accommodate 141 students). Metzger directed the Summer School for four years. He was also the supervisor of the Agricultural Department of the Maryland High Schools for the State Department of Public Instruction and wrote extensively about agricultural education.
In 1917, Metzger became head of the Department of Agronomy and Agronomist of the Experiment Station, holding both positions for over twenty years until his death. Metzger took part in research and experiments that led to development of "beardless" barley, conducted research on a special type of turf grass for golf courses, and was a noted author of bulletins and articles on soil research and other related fields. He was a fellow of the American Association for the Advancement of Science and a member of the American Society of Agronomy, as well as the Academy of Political and Social Sciences. In 1930, Metzger was a United States Representative at the One-Hundredth Anniversary of Natural Nitrates, held at Santiago, Chile.
Active in campus life, Metzger was a member of the Athletic Board and the Scholarship Committee. He also served as president of the University of Maryland chapter of Phi Kappa Phi from 1930 to 1931 and was a president of the University of Maryland Chapter of Sigma Xi, the scientific research society, in 1935. In addition, he was a president of the Prince George's County Kiwanis Club and a member of the Mount Herman Masonic Lodge.
In 1929, the university appointed Metzger Assistant Director of the Maryland Agricultural Experiment Station. When Dr. H. J. Patterson retired as Director of the station in 1937, Metzger assumed this position as Acting Director, while continuing in his position as head of the Department of Agronomy. In June 1939, he became Director of the Maryland Agricultural Experiment Station. Metzger died on December 25, 1939, of a heart attack while on vacation in Florida. He was fifty-seven years old. His wife, Jane (Jennie) Butts Metzger, survived him.