There are many types of metadata. What exactly are you looking to remove? Some methods are as fine as a surgeon's scalpel, while others are broad like a chainsaw. There are a number of options in the following topic, updated code at the end of the thread:
EDIT: Although it is convenient to edit metadata on an open image, it is generally better to use Adobe Bridge scripts to edit metadata as the image data does not have to be processed. Likewise, although possible to batch edit metadata in Photoshop, Bridge is better suited to editing metadata in multiple files.