Amphimacer meter uses a three-syllable foot with a stressed or long syllable on both sides of an unstressed or short syllable: da-DUM-da. In classical prosody, the pattern is long-short-long; in English verse, it is usually described as stressed-unstressed-stressed. Because the rhythm is uncommon in English, poets often use it only in brief passages or as a variation rather than as a whole poem's steady meter.
Example
Silvered rain on the river
Falls and fades into night