Players with 15 Smithing can smelt iron ore into an iron bar by using it on a furnace, granting 12.5 Smithing experience. At level 15, there is a 50% chance of success (-128 profit), increasing by 1% per level, maxing out at 80% at level 45 (117.25 profit). Wearing a ring of forging (185.23 profit) or using the Superheat Item spell (-529 profit) ensures 100% success. Note: A ring of forging only lasts for 140 smelts.
The Blast furnace can be used to smelt the iron ores at a 100% success rate.
An iron bar can be smithed on an anvil through the Smithing skill to create iron weapons and armour, granting 25 Smithing experience per bar used. A list of iron items that can be smithed from iron bars and the Smithing levels required can be found at Smithing/Smithing tables.
It may be more profitable to sell iron ore instead of making it into bars, since the release of Artisan's Workshop increased the demand for ore.