Iron ball

The Iron Balls are objects found throughout Pikmin 3 that serve as an interact-able obstacle, much like the paper bags. They are very plain metallic-grey orbs

Iron balls usually block entrances and exits to other parts of an area. However, with the help of Pikmin, usually around ten, they can be moved out of the way. The balls are always placed at the tip of a slope, so they will rush down once the Pikmin have set them in motion. This allows the player to defeat enemies, though the player's Pikmin can also be crushed if they are in the ball's path. Rock Pikmin will survive the hit.

In other cases the balls do not even block a path, but are there simply to knock a wall down, such as the glass wall in the Formidable Oak or the dirt wall beneath the snowman in the Distant Tundra Once used, the balls serve no further purpose. Usually they disappear off the map.