I’ve read that in comparison to precious metals, Bitcoin is gold & LiteCoin is silver.
This is not relevant anymore. Calling litecoin as a silver is a non sense thing for sure. there was a better coin to be called as silver rather than litecoin. this is why this not relevant. litecoin is just the same like any other altcoin and it doens't even have utility usage. I doubt that to call this as a silver.
Would LiteCoin not be considered Bitcoin’s closest rival?
Litecoin would not be considered as the closest rival for bitcoin but ethereum would. It's caused by litecoin already degrade and i see that people are actively jumping into the new project rather than use litecoin. this is not also store of value like bitcoin.