Similes are where you compare two different things, using the words like or as. So, for example, "my love is like a red rose," or "my love is as constant as the sunshine." When you are looking for similes, keep your eyes open for those tag words of like and as, and it will help you to find them.
In chapter seven of Ethan Frome, Mattie and Ethan's happiness is abruptly ended when Zeena comes home from her trip a bit earlier than expected. Ethan goes upstairs to confront his wife and talk to her about their journey. The first simile comes after they break into an argument--she accuses him of marrying her only out of pity after she helped out with his mother, and he gets upset, and then Wharton writes,
"their thoughts seemed to dart at each other like serpents shooting venom."
This simile symbolizes their angry, hateful mood, and the bitterness of their thoughts for one another. Their thoughts were fierce, angry, darting, and poisonous, like a snake. Just after that, Ethan is ashamed at his thoughts, and thinks that they are as "senseless and savage as a physical fight" between enemies. That is another simile that is mentioned.
A few pages later, Zeena mentions how the townspeople gossip about Mattie being at the house, and that comment is described as "like a knife-cut across the sinews," which cuts Ethan to his core. All of these descriptions serve to intensify and heighten the anxiety and stress that exists between Ethan and his wife. They are strained, but not outright cruel or mean, and the similes serve to enhance that controlled bitterness that they have. I hope that those thoughts helped; good luck!
In chapter 7 Edith has returned from the doctor and her trip. Ethan goes up to the bedroom to see her sitting there. She tells him that she is sicker than he believes. She tells him she has complications which in his day meant bad problems. She tells Ethan that she ahs to have a hired girl because she is to sick to care for the house according to the doctor.
When Zeena is trying to make Ethan feel guilty about losing her health taking care of his mother they look at each other.
"thoughts seemed to dart at each other like serpents shooting venom." (similie)
"senseless and savage as a physical fight between two enemies"
"sounding between them as though a torch of warning "