Link: http://adteputek.com/b2evolution/blog2.php/2009/05/14/2009-05-14-why-use-an-anti-seize-compoun

The goal is to reduce maintenance costs with problems associated with metal to metal contact including corrosion (chemical and environmental) friction, high temperature, load and torque. Anti Seize does all of what grease does but much much better because it has much higher solid content. Solids include Copper, Graphite, Aluminum, Graphite, Ceramic, Molybdenum Disulfide, and Nickel. Solids is what acts as a barrier between the two mated parts and reduces the above mentioned problems. Also, Grease and Oils do not last more than 400 to 500 degrees Fahrenheit before it leaves the parts it is protecting. The Solids continue protecting up to the melting point of the solid, which depending on the formula is between 1800 to 2600 degrees Fahrenheit.