(1 of 2) Nevermind the dubious shopkeeper, this is a very robust shield.
Nevermind the dubious shopkeeper, this is a very robust shield. (left), With it, you don't have to worry about your shield burning. (right)
The Iron Shield is a shield made from tough metal, which can resist flames, but is susceptible to electricity. It has 50% more durability than the Wooden Shield.
When venturing to fiery landscapes, such as Eldin Volcano, you should carry the Iron Shield (or better) with you, unless you want your shield to burn away in your hands.
Where to Find
After completing Skyview Temple, you can buy the Iron Shield from the Skyloft Bazaar for 100 Rupees.
The Iron Shield can be upgraded to the Reinforced Shield.
Alternatively, you can wait until the Sacred Shield is stocked at the Bazaar, after learning the Ballad of the Goddess.