Meter is defined in scansion as the rhythm and the number of repeating patterns. A question about meter excludes structure and rhyme scheme. The meter of Sydney's "My True-Love Hath My Heart" is a classic iambic ( ^ / ) pentameter (five feet of iambs) with elision and proparalepsis adding variation. Line one shows the meter clearly: "My^ true' / -love^ hath' / my^ heart', / and^ I' / have^ his'." Sydney wrote this in a very rhythmic meter; one can almost sing along while reading it if a tune comes to mind. Line two has the first instance of elision. Elision is defined as the omission of a vowel, a consonant, or a syllable in pronunciation of one or more words. The elision in line two occurs in the word "given." Normally, it would be pronounced "gi' -ven^". However when the vowel e in the second syllable is elided the pronunciation changes to "giv'n." It is now pronounced as a single syllable instead of two and fits the meter as the stressed syllable of the final iamb. "By^ just' / ex^ -change' / one^ for' / the^ o' / -ther^ given'."Sydney chose not to illustrate the elision as some authors do (giv'n), but it is elided anyway.
Some might view an alternative scansion to the meter as scanning line two with an incomplete sixth foot. While many poets choose to use incomplete final feet, the convention, which is called catalexis, only applies when an unstressed syllable is dropped from trochaic or dactylic feet. It is also normally used in a patterned meter (except perhaps in free verse) and not as a random line here or there. As a result of these two poetic conventions, elision and catalexis, the alternative scansion turns out not to be an alternative after all. Therefore the correct scansion is that "given" is ellided to "giv'n" and forms the stressed syllable of the final pentameter foot.
The second instance of elision is in line four and is explained the same as line two is: "driven" in the final pentameter foot is elided to "driv'n" to form the final stressed syllable: "There ne' / -ver was' / a bar' / -gain bet' / -ter driven'," with "driven" scanned as "driv'n." In line nine, Sidney uses a technique opposite to elision: he emphasizes a syllable in an alternate pronunciation to the usual one by adding adding a syllable to the end of a word in a technique called proparalepsis. The word "received" may be pronounced as either re^ceived' or re^ceiv^ed^, thus creating three syllables out of a usual two. As an illustration, the same technique of proparalepsis is applied to beloved, and we hear it around Valentine's Day. With proparalepsis, Sidney stretches "receivèd' to three syllables, thus composing five full pentameter feet: "His^ heart' / his^ wound' / re^ -ceiv' / -èd' from' / my^ sight';".