The World is the final card of the Major Arcana, that's why it's associated with completion and endings. It's also associated with distance, journeys and traveling. The Sun card is a symbol of clarity, children, success, vitality, but it also warns against excess, arrogance and burnouts. The combination of the World with the Sun points to a successful conclusion of a matter and it foretells positive energies and satisfaction.
The elements of the cards are Earth (The World) and Fire (the Sun). The cards are equal in strength (both Major Arcana) and the elements are neutral to each other. The Fire card can have a cathartic effect on the Earth card, so the Sun can push away obstacles and delays, while the World offers a solid base for the Sun to realize its potential.