e.g. Denise bought a bracelet that looked great online, but when she got it, she realized that all that glitters is not gold.

Meaning: something that seems attractive and valuable at first might turn out to be worthless

Origin: This expression comes from the late Middle Ages (the 1400s) and teaches us the appearances can be deceiving. This famous saying appears in various forms in many other languages. The great American author O. Henry (1862-1910) wrote a short story about people fooled by what they thought would be a quick way to make lots of money. The story was called "The Gold That Glittered." Gold Miners in the old West in the mid-1800s discovered this lesson the?hard way. Some spotted chunks of glittering yellowish rock and thought that it was gold, but it was only fool's gold, an almost worthless brass-colored mineral called iron pyrite. They were very disappointed, as anyone would be who was attracted by something that appeared to be beautiful or precious but that turned out to be useless junk.

閃光的不全是金子，指某物看似寶貴、迷人，實則毫無價值。源自中世紀(jì)晚期（15世紀(jì)）。