The aim of the contribution is to show that introductory and final formula considered as one of the most phenomenal features of a fairy tale are inwardly structured. These formula were analysed on the base of the ethnographic material (so called Wolman's catalogue of Slovak fairy tales). We analysed them regarding to their construction, way of development, stylisation, attitude of a narrator, measure of convention and a way of its contamination. We identified the several types of these skeleton forms: simple introductory and final formula characterised by a lower degree of stylization and development of conventionalised form and content; stylised introductory formula (magic), an explicitly characterised fictional world of fairy tales; stylised introductory formula (rhetoric) and final (formula with an involvement of a narrator into a plot) formula, expressing an attitude of a narrator to the told story. Further, we found that in the folk environment differently from the literary one, the occurrence of formula in the right sense of word is rarer. It is clear from the analysis that some of the types of formula determine generic characteristic of texts, in which they function like their skeleton; it is also clear how much they also depend on an interpret's narrative characteristics. In the end of the contribution we defined the functions of formula, which are revealed just on the background of typological modification of formula. The basic function of formula is to declare a fairy tale story as a fictional story - that is why we can consider formula as a type of metaleptic figures.