This paper reviews the results of the intense experimental and theoretical studies on the influence of selected metals on the electronic system of biologically important molecules such as benzoic, 2-hydroxybenzoic and 3-pyridine carboxylic acids as well as 5-carboxyuracil. The research involved following techniques: infrared (FT-IR), Raman (FT-Raman), FT-IR Ar matrix, electronic absorption spectroscopy (UV/visible), nuclear magnetic resonance ((1)H, (13)C, (15)N, (17)O NMR), X-ray and quantum mechanical calculations. The influence of metals on the electronic system was examined through comparison of the changes in so called "logical series". The exemplary series are: Li-->Na-->K-->Rb-->Cs, Na(I)-->Ca(II)-->La(III)-->Th(IV); Na(I)-->Mg(II)-->Al(III) or long series of La(III) and fourteen lanthanides La(III)-->Ce(III)-->Lu(III). The correlation between the perturbation of the electronic system of ligands and the position of metals in the periodic table was found. The influence of the carboxylic anion structure and the effect of hydration on the perturbation of the electronic system of molecule were also discussed. The partial explanation in what way metals disturb and stabilize electronic system of studied ligands was done. It is necessary to carry out the physico-chemical studies of benzoates, salicylates, 3-pyridine carboxylates and isoorotates in order to understand the nature of the interactions of these compounds with their biological targets (e.g., receptors in the cell or important cell components). The results of this study make possible to predict some properties of a molecule, such as its reactivity, durability of complex compounds, and kinship to enzymes.