in the book east of eden does the author use metaphoric or ironic devices

Okay, I'm pretty sure you mean "devices". I think there is a lot of metaphor in the novel. He specifically uses allusions to the Bible. Consider the story of Cain and Abel. The Trask family becomes a metaphor for the biblical story of Cain and Abel. Consider Charles and Adam. Like the Biblical story, Charles grows jealous of his brother Adam and attacks him in a fit of rage. Similarly Adam's sons, Cal and Aron, have their own feud. Charles's scar is also symbolic for the “mark of Cain” in the Old Testament story. There is also some irony in the character of Lee. It is both situational and verbal irony. Lee is considered inferior in intellect. He is instead a scholar at heart. He remains a constant friend to Samuel Hamilton and Adam Trask, aiding them in their scholarly debates. He researches the Cain and Abel story and proffers the novel's central concept of "thou mayest."