In "Oh, my love is like a red, red rose" what is an example of a metaphor in the poem?

Let us remember that a metaphor is different from a simile
in that it asserts a comparison between an object and something else directly, without
using the words "like" or "as." Of course, this poem is most famous for how the
speaker's love is "like" a red rose, which is a simile, but if we look carefully we can
see that there is an implied metaphor used in the third
stanza:

Till
all the seas go dry, my Dear,
And the rocks melt with the sun!
O I
will love you still, my Dear,
While the sands of life shall
run.

"The sands of life" is a
metaphor as it compares life and the allotted span that each of us have to a sand timer,
which is constantly allowing sand to run from the top chamber to the bottom chamber,
indicating how much life we have left and also symbolising the life we have in the
"running" of the sand. The metaphor thus reinforces the speaker's love for his beloved,
by emphasising the way that his love will continue whilst he has breath in his
body.