Last in the series of classical elements is fire--which, once again, you can interpret literally or metaphorically. Fire is heat and flames and burning fuel, of course--also the sun. Fire is traditionally associated with the qualities of energy, assertiveness, and passion. Some more of the metaphorical meanings of fire are discussed here and here.
Thanks for humoring me during this exploration of the four elements. =smile= Next month, our themes will be hosted by the illustrious Vivienne Strauss.