It is shown that the indefinite metric structures of degenerate systems as given by Strocchi and Wightman [F. Strocchi and A. S. Wightman, J. Math. Phys. 15, 2198 (1974); 17, 1930 (1976)] arise in a natural fashion from the algebraic structure of such systems, where the latter has been developed in a C*-context by Grundling and Hurst [H. B. G. S Grundling and C. A. Hurst, Commun. Math. Phys. 98, 369 (1985)]. Auxiliary concepts like gauge equivalence are examined, and the preceding general theory is specialized to the situation of linear boson fields with linear Hermitian constraints. Two examples of this situation are given—a one-dimensional scalar boson in a periodic universe and Landau gauge electromagnetism.