Embodiments of movable weights, such as weight plugs and other types of movable weights, for a golf club head are disclosed herein. One embodiment for a weight plug, for example, includes a mass element with a first end that has a threaded portion and a second end. The weight plug also has a weight cap with a seal retention portion that is configured to engage a seal. The cap is also configured to engage the threaded portion of the mass element. A seal is positioned between the first end of the mass element and the seal retention portion of the cap.