A sword is a magickal tool used by some practitioners to direct energy much the same way the wand, athame or staff.
The use of the sword as a magickal tool is rooted in Western ceremonial tradition and is generally considered a tool for formal occasions.
Sword Correspondence
The sword is masculine in nature and different traditions assign different elemental correspondence to it.
Generally, those who lean more toward the ceremonial magick influence correspond the sword to the element of air while those with more folk magick influence correspond it to the element of fire.
Ritual Uses for Swords
During magickal ritual, a sword can be used much the same way you might see a sword used during other ritual situations- to salute, to honor, to bless and as part of initiations when individuals may be symbolically slain in preparation for their rebirth in a new role.