Massage melts are a unique body product because they stay solid at room temperatures, but when applied directly to your skin, start to soften and melt due to body temperature. Their main purpose is to moisturize dry skin, as well as, relax and soothe tight muscles.
Essentially, massage bars are composed of natural butters and oils. Most recipes for this type of product call for the use of cocoa butter. Even though it has great moisturizing properties, I feel this butter produces too hard a product. Therefore, I recommend using such butters as shea and mango, which create a silkier, luxurious feeling to your melts.
For oils, I highly recommend using sweet almond and jojoba. Sweet almond oil is light and penetrates easily making it well-suited for dry skin conditions. Plus, it is effective on all skin types. Jojoba oil, which is not actually an oil but is a liquid wax, is similar in composition to the oil your skin secretes, which is known as sebum. Jojoba is a quickly absorbed oil that soothes the skin, as well as, extends the shelf life of other oils.
Other light oils you can substitute, for the above, are apricot kernel, grapeseed, sunflower, safflower,...