While Emily Dickinson most dominantly used personification, symbolism, and imagery in her poem "Because I could not stop for Death--," we certainly can see a couple of uses of metaphor and simile.
One example of a metaphor can be found in the first stanza with respect to the carriage. The carriage driven by Death is not literally a carriage but rather a metaphor for life's journey that ends in death and of passing from life into the new state of death. Similarly to ancient mythology, the carriage represents a way of being taken to the underworld, just as the Ancient Greek god Charon transported deceased souls to Hades in a ferry on the river Styx. We can tell the carriage is not an average carriage because it "held but just Ourselves--/ And Immortality." Death can be seen as an endless life and, therefore, as an immortal life. Hence, since the carriage is not an average carriage, we know it is representative of a larger idea. More specifically, it represents the ferry of Ancient Greek mythology, and both are metaphors for the passage of life into death, as if transitioning into death was like taking a ride in a carriage.
A simile can be found in the second-to-last stanza in which she describes the house they stopped at as "seemed / a Swelling of the Ground--," meaning a house that looked like swollen ground, kind of like a mound, more specifically, a burial mound. Hence by using the verb "seemed," she is comparing the house to a burial mound.
The "House" itself is also another metaphor. Its not a literal house they have stopped before. Instead, the term house refers to the afterlife idea of a house in the Kingdom of Heaven, an idea we get from the Gospel of John in which Jesus, during the Last Supper, tells his disciples he is preparing a place for them in his Father's house in the Kingdom of Heaven:
In My Father's house are many dwelling places; if it were not so, I would have told you; for I go to prepare a place for you. (John 14:2, NASB)
Hence, by using the term "House," Dickinson is comparing the afterlife to a dwelling place, like a house and metaphorically representing the afterlife as a "House." Yet, the "House" is also submerged in the ground, just like a tombstone; therefore, we also know it is metaphorically representing a tombstone.