In part one, Mephistopheles says to Faust, "Dear friend, all theory is gray, / And green the golden tree of life." In this quotation we have our first literary device, namely the color imagery of "gray," "green," and "golden," and also a second device with the metaphor "tree of life." The color imagery is used by Mephistopheles to convince Faust to turn from his studies, which are, as "gray" connotes, lifeless and dispiriting, and instead turn towards a life of hedonistic experiences, which are vibrant and enriching, as connoted by "green" and "golden." The metaphor "tree of life" is perhaps an allusion (a third literary device) to the garden of Eden story, where Satan, in the guise of a snake, persuaded Adam and Eve to eat from the forbidden tree of knowledge. Mephistopheles is attempting to do much the same here. He is trying to tempt Faust into an irreligious life of the senses and out of the favor of God.
Also in part one, Mephistopheles says to Faust, "Forbear to trifle longer with thy grief, / Which, vulture-like, consumes thee in this den." In this quotation, the literary device is the simile comparing Faust's misery to a vulture. A vulture is a scavenger bird which feeds upon carrion, and so here Mephistopheles is suggesting that Faust is allowing his misery to feed upon him, like a parasite, and also that as long as he allows his misery to eat away at his body, he will, to all intents and purposes, and just like the carrion that the vulture feeds upon, be dead. In this way, Mephistopheles hopes to persuade Faust to turn from his studies and to a life of hedonism.
In part two, Sorge says to Faust: “Throughout their whole existence men are blind; So, Faust, be thou like them at last.” In this quotation, the metaphor "men are blind" suggests that men cannot see what truly matters. At this point in the story, Faust, having grown tired with the limitations of his studies, doesn't quite realize that his hedonistic activity also has its limitations. Sorge is trying to warn him to pay more attention to the spiritual and the sacred and not to be wholly distracted by the meaningless illusions that Mephistopheles presents to him.
Another quotation from part two, also including the literary device of metaphor, is:
The world has always been the same -
An endless farce, an antic game,
A universal masquerade!
In this quotation the idea that the world is, metaphorically, a "masquerade" is reminiscent of the famous assertion from Shakespeare's As You Like It, that "all the world's a stage, / And all the men and women merely players." Both metaphors, from Goethe and Shakespeare respectively, imply that there is no substance, or no meaningful reality, behind the facade of human life. In the case of Faust, the specific implication is that his life of hedonism is devoid of all meaning. He has made his life into a "farce" and a "game." The masculine end rhymes ("same ... game ... masquerade") lend to the lines a singsong, playful tone, echoing the triviality and childish silliness that now characterize Faust's life.