As a verb alight means for a flying insect or animal to land or perch after flying. This definition can extend to anything descending upon or landing on something. It can also mean for a person to depart or exit a mode of transportation. Archaically alight meant to acquire or meet something or someone by chance, its noun form was alightment.
As an adjective, alight means to be on fire or shining with lights. The on fire definition is predominantly used in the United Kingdom, though it can be seen other places as well. This definition exists figuratively as well (i.e., if something can be figuratively on fire, it can also be figuratively alight).
A watercolour of a flight of eight shelducks alighting on estuary sands by Norfolk artist John Cyril Harrison (1898-1985) is estimated at £800-£1,200. [Daily Post]
Our backyard is a flurry of tiny aviators, zipping and humming, darting and sipping, diving and reversing; chasing each other and alighting on tree limbs, potted plants, porch posts, a porch swing chain, flowering plants and, of course, our red nectar feeders. [Gadsden Times]
And her gaze alights on anything with a pattern. [W Magazine]
Bentong police chief Supt Mohamad Nor Mansor said, when Chan alighted from the vehicle to inspect the damage, two men armed with knives rushed out of the other car and demanded for his wallet. [The Malay Mail Online]
The early evening sky is alight with crystallizing stars, probably more than I’d see in the dead of Manhattan night. [Brown Daily Herald]
The phenomenon has also reached the US where the Gujarati community is alight with the Baka meme. [Times of India]