Inconsistencies in the metal-hydrogen (M-H) systems literature relating to the use of the partial configurational entropy for hydrogen absorbed in a metal are examined, and the usefulness for M-H systems of the partial excess entropy is questioned. Treatment of the behavior of M-H systems in terms of chemical solution thermodynamics is considered and it is concluded that this approach does not provide an appropriate representation of the special properties of an M-H system; many of these properties are usefully represented by a lattice gas model. An example is given of combining the configurational entropy of a lattice gas, with a summation of the principal changes to the entropies of the lattice-related and electronic subsystems of the metal lattice, resulting from the absorption of hydrogen. Rough estimates of quantitative values for such contributions are made based on experimental data. This summation of contributions is a practical and conceptually useful method for determining the entropy change produced by the formation of an M-H system.