ものだ

ものだ expresses general truths, norms, or common-sense expectations. It makes statements about what is considered natural or proper in a given situation. It can convey a sense of recommendation or social custom, as well as general observations about life. In many cases it uses the plain form of verbs and adjectives and sounds somewhat formal or literary. The nuance differs from direct advice like べきだ in that ものだ presents a conventional belief or generally observed fact rather than a direct command. It can also express a calm, reflective tone when stating what tends to be true.