Are the other examples of the theme "all that glisters is not gold" in "The Merchant of Venice?"I can only think of Portia's casket test.

(Not wishing to nit pick, but the exact line is, 'All that glisters is not gold...')

I suppose this phrase warns us that we should be careful of accepting easy first impressions and shallow judgements about situations and people. MoV is obviously about the clash of race and religion, so there are many examples that would fit.

Should we see Shylock as simply 'An Evil Jew' who lends money and plots against the 'golden' Antonio, the Christian. If we look more closely at the situation, we can see Antonio is not so perfect or good, not so golden.

Or the loan of 3000 ducats with the unusual contract... more careful consideration by Antonio would have revealed its less than golden appearance.

And Antonio is not worried about the contract because he says he's got lots of ships coming from all over the world, so he's a rich man who will repay easily... but they all sink, so his golden business plans are not what they appear.