Let's look at Frost's short poem, "Nothing Gold Can Stay." It is quite potent, to use your word, because the language is so condensed. He says so much with so few words.
We can understand the first line to be figurative because "green" cannot literally be "gold," so we can begin to consider what this line might mean. Gold is something which is very valuable, and so perhaps the speaker is suggesting that the "first green" is the most valuable thing; this is a metaphor. But what is the "first green"? He says that it is the "hardest hue to hold." So, it passes quickly.
"Her early leaf's a flower," the speaker says, but how can a leaf be a flower? This must be figurative too, especially because it only lasts an "hour." So, a flower is compared to a leaf, via metaphor, because it is the first thing to bud on a plant, the first stage of a life. "Then leaf subsides to leaf," so the "early leaf" that is really a flower goes away and the plant grows real leaves. Flowers bloom first, and then leaves grow in great number as the seasons pass and the plants grow older.
Then, however, the speaker says that "Eden sank to grief," apparently alluding to the loss of innocence that caused Adam and Eve to fall from God's grace in the book of Genesis, the first book of the Old Testament of the Bible. As we age, we lose our innocence (and youth), and we absolutely cannot hold on to these things because "Nothing gold can stay." Nothing truly valuable—things like youth and innocence—can remain forever. So, we see that nature's "first green" is actually a metaphor for youth and innocence: the things that are so valuable but impossible to hold on to.
Throughout this poem, then, Frost achieves a wistfulness for the innocence that none of us can ever reclaim. He creates a mood of inevitability, that we will all, if we live long enough, outlive our youth and innocence. He creates a sense of foreboding as well, as a result of this inevitability. The most valuable things will always leave. Through his uses of metaphor and other figurative language, Frost creates a potency that could not be achieved with more words.