modus.irrealis wrote:
... My big problem was getting a sense for the rhythm of the poetry (basically, I can't tell why it is poetry) and it's something I'd really like to understand so I was hoping someone here had some tips for me on how to get this feeling for the metre.
I'm okay with lines where all heavy syllables are caused by long vowels, and I think my main problem is with figuring out how a closed syllable (especially one that ends in a stop) can be heavy. Is it simply convention and I just have to adjust my thinking, or is there a phonetic basis for all this?
As William points out there is indeed a phonetic basis. Quantitative meter is about durations (time), so when a "closed syllable" is marked as long it's because it is actually longer in sound, it takes longer to articulate than a syllable with only one short vowel sound. Consonants also lengthen the amount of time required for the syllable.
The problem for most readers lies in the fact that quantity is not a structural basis for the poetry with which we're most familiar, so getting the right feel for quantity takes some effort. My Latin teacher made me read newpaper items in meter, i.e. I'd superimpose a particular scansion on the prose text and try to read it in meter.
In the end you'll have to practice reading aloud and paying close attention to the actual sounding lengths as heard in good readings.
Btw, the subtleties afforded by quantitative structures are very hard to reproduce in English. Yes, of course we have quantity, but we do not organize our meters by it, and many quantitative effects are simply unlikely in a language such as English.
In Latin at least there is also a play of word accent against the rhythm established by the quantity. I'm not yet as facile as I'd like to be with the Homeric hexameter, but I can read it well enough to affirm that is is indeed poetry.
Just keep practicing and listening. You're cultivating a finer sense of time when you learn quantitative metrics, so a musical sense is good to have too, but just keep at it, you'll get it. It's all a matter of time.

Similis sum folio de quo ludunt venti.