Regarding "To Sir John Lade, on His Coming of Age" (‘A Short Song of Congratulation’) by Samuel Johnson, when looking for a connection between form and content, my first inclination is to look at the "sound" of the poem. (Remember, poems were always meant to be read aloud so as to hear the many devices the poet used in the poem's construction.)
Looking to the meter (rhythm) of the poem is the first important element in studying the poem's "sound" because it is so obvious. The meter is...
...a rhythm of accented and unaccented syllables which are organized into patterns called feet.
...trochaic meter is a foot consisting of an accented and unaccented syllable.
"To Sir John Lade, on His Coming of Age" then is written with a trochaic meter.
The poem also has a set rhyme scheme. A rhyme scheme is...
...the pattern of rhyme used in a poem, generally indicated by matching lowercase letters to show which lines rhyme. The letter "a" notes the first line, and all other lines rhyming with the first line. The first line that does not rhyme with the first, or "a" line, and all others that rhyme with this line, is noted by the letter "b", and so on.
Johnson's rhyme scheme follows the rhyming pattern of ABAB. In other words, the first and third lines rhyme, and the second and fourth lines rhyme; this pattern continues throughout the poem.
The rhyming pattern also provides a sense of movement.
After analyzing what I hear when I read the poem, I look then to the poem's content. Johnson tells the story of Sir John Lade, a young man who has inherited a seemingly large fortune, whereupon he systematically goes around dropping cash in one place and then another, moving from one form of "dissipation" to the next.
While the meter gives a sense of his movement from one kind of entertainment to another—as Lade continues losing cash all the while—the meter of the poem also gives the sense of chopping: the cutting up his assets, such as houses and land, which (as Johnson notes) mean nothing more than wet or dry land to Lade. It also gives the sense of chunks of cash being squandered here and there, disappearing forever in someone else's willing hands.
It is in these ways that I feel Johnson uses the structure of his poem to support the content of his poem. (This is, by the way, a wonderful poem, not only for its content, but also its form.)