The Lottery contains several symbols that contribute to the work's entire meaning.
A first symbol to consider is the stones. In the beginning of the story, the very stones that the children play with for fun will later be used for the greatest possible destruction. These stones symbolize the power of life from beginning to end. In the beginning, life is simple, playful. As time goes on it becomes more complex and ultimately destructive. AS we age, our abilities to hurt each other increase. Our willingness to destroy each other increases.
A second and more important symbol is the black box itself. This color obviously symbolizes evil, but the features of the box represent the tradition that has remain unchanged. This box has seen incredible amounts of time. It is only used once a year, yet it is damaged.
The slips of paper represent each person, but beyond that these slips represent chance.
Names of many characters represents factors about them that hold irony. For example, "Graves" would symbolize death, "Summers" symbolizes the hope of the time of year.
The summer solstice is when the great event of the lottery occurs. For many, this is the longest day of the year just in terms of time. Literally and figuratively, for whoever "wins" the lottery, this day can become an eternity... in heaven or hell.