What are some similes and metaphors in "The Lottery" by Shirley Jackson?

The only example of simile in "The Lottery"—and a particularly weak one at that—is when Mrs. Hutchinson taps Mrs. Delacroix on the arm "as a farewell." This could reasonably be interpreted as a simile in that two dissimilar things are being compared using the word "as."
In terms of metaphor, the black box used to draw the "winning" names represents death. Again, death and a black box are two completely dissimilar things, yet in the overall context of the story, the box is a metaphor for death because the unfortunate individuals whose names are chosen from it will be sacrificed as part of this annual pagan ritual.
Old Man Warner can be seen as a metaphor for unthinking devotion to tradition. At no point has he ever stopped to consider the sheer, unadulterated barbarism of the ritual in which he's been such an enthusiastic participant over the years. In fact, Old Man Warner has become so deeply attached to the lottery tradition that he thinks it outrageous that the younger generation in neighboring villages have started giving up the old ways.

There are no obvious similes in the story, and there are no particularly obvious metaphors either. There are, however, some implicit comparisons which can be deemed similes and some figures of speech which might be considered metaphorical.
For example, commenting on how frequently the lottery seems to come around each year, Mrs. Delacroix says, "Seems like we got through with the last one only last week," and Mrs. Graves replies, "Time sure goes fast." The words "seems like" indicates that Mrs. Delacroix is comparing her impression that time has gone quickly with the time frame of one week. This simile helps us to understand just how short the year since the previous lottery seems to have been for those who have to participate in it.
Early in the story, Jackson writes that on the morning of the lottery, "the feeling of liberty sat uneasily on most," referring to the school children who had only recently finished school for the summer. They were not yet used to their freedom or liberty, and thus the "feeling of liberty" is said to have "sat uneasily" upon them. This feeling, of course, did not literally sit upon the children, but using this metaphorical language helps to convey the sense of weight and discomfort that the children felt. They had become so accustomed to the school routine that anything different felt at first unusual and uncomfortable, like a weight that's awkward to hold.

A metaphor is a comparison that does not use the words "like" or "as."
The shabby and splintered box that holds the lottery tickets is a metaphor for the increasingly worn and outdated lottery ritual. The black color of the box can be compared to the darkness of the lottery, which ends in the death of a community member at the hands of his or her neighbors. The refusal to repair the box can be likened to the denial the village residents seem to be in about the lottery. Like the box, they are caught in a limbo between wanting to hold onto an outmoded tradition and knowing down deep they need to change.
Old Man Warner likens giving up the tradition of the lottery, which to his mind promotes social stability and prosperity, to living in caves, implying that the loss of the lottery would lead to barbarism.

Shirley Jackson's writing style in "The Lottery" does not utilize much figurative language; there are no similes. However, there are a couple of metaphors in the protests of Old Man Warner.
Old Man Warner defends the existence of the annual lottery, disdainfully remarking "they'll be wanting to go back to living in caves" with regard to its critics. His exaggeration is a metaphor; he does not literally mean that the community will regress to that extent, but he clearly has strong feelings about retaining the tradition of the lottery.
Warner follows up his disdainful remark with another: "first thing you know, we'd all be eating stewed chickweed and acorns." Chickweed is, as the name suggests, a weed, or an uncultivated plant generally not consumed as food. Acorns are eaten by undomesticated animals, and this comment follows up on his idea that discontinuing the lottery will have a negative influence on the civilization of the community.