Iron and manganese ions with terminal oxo and hydroxo ligands are discovered as key intermediates in several synthetic and biochemical catalytic cycles. Since many of these species possess vigorous catalytic abilities, they are extremely transient in nature and experiments which probe the structure and bonding on such elusive species are still rare. We present here comprehensive computational studies on eight iron and manganese oxo and hydroxo (Fe^III/IV/V-O, Fe^III-OH and Mn^III/IV/V-O, Mn^III-OH) species using dispersion corrected (B3LYP-D2) density functional method. By computing all the possible spin states for these eight species, we set out to determine the ground state S value of these species; and later on employing MO analysis, we have analysed the bonding aspects which contribute to the high reactivity of these species. Direct structural comparison to iron and manganese-oxo species are made and the observed similarity and differences among them are attributed to the intricate metal–oxygen bonding. By thoroughly probing the bonding in all these species, their reactivity towards common chemical reactions such as C–H activation and oxygen atom transfer are discussed.