The combustion of iron at high oxygen pressure in normal gravity and microgravity was investigated. Cylindrical rods 3.81- to 11.43-cm long, with diameters of 0.10, 0.20, and 0.32 cm, were burned in 100% gaseous oxygen, in normal gravity and microgravity, and the results were compared and contrasted. Two types of tests were conducted: 1) gravitational gradient tests and 2) microgravity combustion tests. The gravitational gradient test results showed that burning iron rods do not extinguish with a reduction in the gravity level, and may, in view of an observed increase in the consumption rate of the rod, have combustion enhanced in microgravity environments. The microgravity tests showed that the same dependency exists between rod diameter, oxygen pressure, and regression of the melting interface in normal gravity as in the microgravity combustion of iron rods: as the oxygen pressure is decreased, or the rod diameter increased, the regression of the melting interface decreased. The dominant processes in the combustion of metal rods are circulation of the metal, oxygen, and combustion products in the molten ball, and heat transfer to the solid rod. This circulation in the molten ball is not controlled by buoyancy, but is believed to be produced primarily due to differences in surface tension.