The cauldron is an essential in Celtic magick. It represents the element of Water. The cauldron is mentioned in many Celtic myths (most notably Cerridwen's story) and is always connected with magickal happenings. Black cast iron is best and most traditional material, although it can be of other metals. Filled with water it can be used as a scrying tool, similar to a magick mirror or a crystal balll. During certain spells candles are set in it and allowed to burn out. It is an all purpose tool; a vital part of your Celtic spellworkings.
The Wicca see the cauldron as a symbol of the Goddess, the manifested essence of femininity and fertility. Ideally the cauldron should rest on three legs, its opening smaller than its widest part. Cauldrons can be difficult to find, and expensive when found.