Picture
Background
A popular use of the subject proverb was in Shakespeare's The Merchant of Venice, which was written in 1596. 

Meaning "All that glitters is not gold" is to say that all may not be as it appears to be. Literally, it means that just because something sparkles or glitters, that does not mean it is gold. It could be some other metal or something that sparkles similarly to gold. In real life, it is easier to apply. For example, if someone appears to be your friend as they treat you nicely and act favorably to you, this does not necessarily mean that they are really your friend and hold your best interests at heart.  You can, of course, also apply it to items or products that look or sound valuable, but can be worthless.

Exampleso
  • Don't be deceived by the designers' dresses, shoes and jewellery that Mary wears. The fact is she is on the verge of bankruptcy. All that glisters is not gold.
  • Don't listen to what the investment consultant told you. She claimed the mini-bonds were as safe as government bonds, but she did not tell you that they could become worthless. All that glisters is not gold

Remarks
Question
Glitters appear to be a plural noun,  why is it not "All those glitters are not gold"?
Answer:     Glitters is not a noun here. It is a verb. All in this situation should be followed by a singular verb as in "All is well". "that glitters" forms a verb clause. If you still cannot figure that out, please try treat it as "All (which glitters) is not gold".

背景
这语句最为人熟识是娄似句子曾在沙士比亚名著威尼斯商人 (1596) 出现过。

意义
这语句直译为“所有闪光的不都是金”。意思是一般事物都不是如外表看上去一样,从字面上来看是指闪烁的东西不一定是黄金,那可能祗是一些跟黄金相似可发光之物体。在真实人生很容易遇到有关例子。例如有些人表面是你的朋友,对你很好,友善及迁就你,这并不意味着他是你真正的朋友。这语法也适用於形容某些物品表面看似值钱,但其实是一毛不值。

例子
  • 你看她穿着名牌服装,皮鞋及珠宝,但不要被他蒙闭,其实她面临破产边缘,人不可以貌相,
  • 请不要听那位投资顾问所说,她声称迷你债券稳如证府债券,但她没有告诉你它们可以变为一文不值,物不可信包装。