Selective functionalization of unactivated C-H bonds, water oxidation, and dioxygen reduction are extremely important reactions in the context of finding energy carriers and conversion processes that are alternatives to the current fossil-based oil energy. A range of metalloenzmes achieve these challenging tasks in biology by using cheap and abundant transition metals, such as iron, copper, and manganese. High-valent metal-oxo and metal-dioxygen (superoxo, peroxo, and hydroperoxo) cores act as active intermediates in many of these processes. The generation of well-described model compounds can provide vital insights into the mechanisms of such enzymatic reactions. This perspective provides a focused rather than comprehensive review of the recent advances, in the chemistry of biomimetic high-valent metal-oxo and metal-dioxygen complexes, which can be related to our understanding of the biological systems.