If you have a surplus of one particular resource, you can trade away that resource with the other players, then use the Monopoly card to collect back everything you traded (and then some).
There is one final power-play you can make with the Monopoly card. If you have a surplus of one particular resource, you can trade away that resource with the other players, then use the Monopoly card to collect back everything you traded (and then some). This can be a very effective move, but will also make everyone else at the table absolutely hate you, so if you do attempt this make sure that you win the game shortly afterwards.