Changing the properties of the feedstock and the addition of fluxes lead to a change in the structure and metallurgical properties of the pellets: reducibility, strength during recovery, softening and melting temperatures. Porosity has a special influence on the formation of the quality of pellets, the nature of which determines both the mechanical properties and the rate of reduction in the conditions of a blast furnace and a metallization module. It has been shown that the porosity of calcined pellets is formed at the granulation stage, and during calcination, its change is associated only with the formation of voids at the site of the removed volatile components, for example, CO2 fluxes. With an increase in the dosage of fluxes, the proportion of pores from the decomposition of carbonates increases to 25% of the total mass of volatiles removed during roasting and up to 15% (rel.) of the total volume of the pellet pore space. The formation of the pore space is determined by the content of waste rock and the amount of fluxes, while the increase in porosity will not necessarily contribute to the increase in reducibility. This necessitates testing of calcined pellets for metallurgical properties even in the presence of data on their porosity. In addition, the extrapolation of the results of the study of pellets from concentrates “poor” in iron to pellets from concentrates of a high degree of enrichment is incorrect, since the scale of the pore space changes.