Literary/written register, common in poetry and descriptive prose. Spoken Chinese prefers 像 (xiàng) or 好像 (hǎoxiàng). Often used to introduce a vivid metaphor.
usage
Synonyms: 宛如 (wǎnrú), 仿佛 (fǎngfú), 犹如 (yóurú). All four are interchangeable in most literary contexts; 宛若 has the softest, most poetic feel.