Short note on the iambic meter
[Confession: I totally suck at ‘feeling’/hearing poetic rhythm :)
The iambic feet refers to a very light beat (unstressed) followed by a heavier one (stressed). This poem after being ‘scanned’ can be seen to have four (tetra) feet per line, hence an iambic tetrameter.
She was / a Phan / tom of / delight
When first / she gleamed / upon / my sight;
Most lyrical English verse is written with iambic meter, hence giving it a kind of musical sing-song quality.