Unlike other chests found in the game, Goddess Chests cannot be opened until Link has activated its corresponding Goddess Cube on The Surface using a Skyward Strike. There are a total of 27 Goddess Chests in the game. Like the Goddess Cubes, the 27 Goddess Chests where placed in The Sky by the Goddess for her chosen hero and thus they contain many items to aid Link on his quest. These include valuable items such as various Medals, Piece of Heart, an extra Adventure Pouch, an Empty Bottle, a Small Seed Satchel, a Small Bomb Bag, and Small Quiver. Some of them contain high value Silver and Gold Rupees.
Until their corresponding Goddess Cube is activated, Goddess Chests remain in a dominant state and cannot not be opened. Only once their Goddess Cube is activated, their color changes and the chest are activated allowing Link to obtain their contents. Upon returning to the Sky after activating his first Goddess Cube, Fi will detect the chest it activated and mark their location on Link's map, to show him where the chest can be found. She will due this automatically for every Goddess Chest Link activates, making tracking them down easier.
Depending on their location, some chests may require Link to obtain a specific item (like the Water Dragon's Scale, Clawshots, or Mogma Mitts) and/or reach a certain point in the game in order to reach the chest itself.
Goddess Chests appear to be made of the same material as Goddess Cubes, Goddess Crests, and Goddess Walls. As they were likely created by Hylia, they may be made of a divine substance that is sensitive to the energy produced by the Skyward Strike (as striking a Goddess Cube with said energy activates its corresponding Goddess Chest). This material may also connect the Goddess Cubes with their corresponding Goddess Chests.