"The Psalm of Life" by Henry Wadsworth Longfellow is a poem which encourages its readers to live a good and moral life, so the title itself is an allusion to the psalms of the Bible. In the first line, that biblical allusion continues with "Tell me not, in mournful numbers..." alluding to the Bible's Book of Numbers.
From there, we find metaphors and personification. First, life is compared to an "empty dream" (a metaphor); and "For the soul is dead that slumbers" personifies the soul.
Parallelism comes to play in the second and final stanzas: "Life is real! Life is earnest!" And "Still achieving, still pursuing."
More metaphors, as well as similes, are found throughout the piece. Hearts are compared (simile) to drums in the fourth stanza, and people are compared (simile) to cattle in the fifth. "Art is long and Time is fleeting" is a metaphor.
Finally, this poem contains quite a bit of alliteration: "Find us further" is one example. "Dumb driven cattle" is another.