ASTM G124, Standard Test Method for Determining the Combustion Behavior of Metallic Materials in Oxygen-Enriched Atmospheres, relies on a pyrotechnical promoter for igniting the tested sample. For more than 10 years, PIMM Laboratory (French National Centre for Scientific Research) and Air Liquide have been investigating a laser-ignition promoter to study both the ignition and combustion behaviors of metals in gaseous oxygen (GOX). A laser irradiates the sample while a fast camera, calibrated as an optical pyrometer, monitors the behavior of the sample during the ignition genesis and combustion propagation. Thousands of tests performed on various sample geometries, including particles, rods and discs, have demonstrated the advantages of this method, such as accurate knowledge of the heat input absorbed by sample prior ignition (and thus the sample's ignition characteristics as ignition temperature and minimum ignition energy, or MIE, to trigger the sustained combustion) and the accurate propagation behavior assessment based on fast camera recording, the sample burn-length measurement, and the burn criterion taking into account metal burned beyond the heat-affected zone (HAZ) created by laser ignition. This paper presents laser-ignition tests carried out on rod and disc samples made of pure iron, carbon steel, and stainless steel. Rod samples were laser-ignited at the bottom of the rod, with an upward combustion propagation, in GOX at atmospheric pressure. Disc samples were laser-ignited in the center of the sample. A comparison of the results from these two sample geometries is presented regarding the MIE required for ignition and sustained propagation, the ignition temperature, the propagation rate, and the final extension of oxygen fire propagation. A numerical model supports the interpretation of results in terms of the HAZ and sample's geometry. Results are discussed and compared to those obtained by the standard ASTM G124 test method.