The Earth's extraterrestrial dust flux includes a wide variety of dust particles that include FeNi metallic
grains. During their atmospheric entry iron micrometeoroids melt and oxidize to form cosmic
spherules termed I-type spherules. These particles are chemically resistant and readily collected by
magnetic separation and are thus the most likely micrometeorites to be recovered from modern and
ancient sediments. Understanding their behavior during atmospheric entry is crucial in constraining
their abundance relative to other particle types and the nature of the zodiacal dust population at 1
AU. This paper presents numerical simulations of the atmospheric entry heating of iron meteoroids in
order to investigate the abundance and nature of these materials. The results indicate that iron
micrometeoroids experience peak temperatures 300-800K higher than silicate particles explaining the
rarity of unmelted iron particles which can only be present at sizes of <50 m. The lower evaporation
rates of liquid iron oxide leads to greater survival of iron particles compared with silicates, which
enhances their abundance amongst micrometeorites by a factor of 2. The abundance of I-types is
shown to be broadly consistent with the abundance and size of metal in ordinary chondrites and the
current day flux of ordinary chondrite-derived MMs arriving at Earth. Furthermore, carbonaceous
asteroids and cometary dust are suggested to make negligible contributions to the I-type spherule
flux. Events involving such objects, therefore, cannot be recognized from I-type spherule abundances
in the geological record.