From Zelda Legends Wiki
As the name says, the Iron Boots are boots made of tough iron. Even the strongest wind can't push these boots away.
When the Iron Boots are used in water, Link falls down to the bottom of the water and is able to walk there. If a wind is trying to blow Link away, he can equip it to prevent the wind from pushing him away.
How the Iron Boots are used
This shows how the Iron Boots are used in the different games.
The Wind Waker
When Link is going to the Wind Temple, he first needs to go through the strong wind- blowing statues. The Iron Boots are used in Wind Waker to prevent the wind from pushing Link to somewhere.
Link can walk on the electric paths located in the Goron Mines. The Iron Boots are also used to go down the water and get to the bottom of the floor/water. The boots are also used when dueling against the Gorons in sumo.