Sorry @b241d2533f05270576b6,I have no idea (actually, I do not understand your question, because ERC-20 is not a one token, but all tokens developed on ethereum standard. And of cause to make any transactions on Metamask you need to pay the gas fees with Eth, as it’s only acceptable payment for fees. If you do not have any Eth you can do any transaction) Just didn’t want you to be hacked.
Hey @b241d2533f05270576b6, you will need MATIC on Polygon to pay for the gas fees. ETH is for the gas fees on Ethereum and MATIC is for the gas fees on Polygon.
Okay actually you are confusing two different networks as well as coins with tokens.
In order to use opensea for buying and selling NFT you either have to pay gas fee in ETH if you choose ETH network or you have to pay gas fee in Matic if you choose matic/polygon network.
You cannot pay gas fee from a token. As token itself requires a gas fee of that network to transfer from one wallet to another.
So advice is, either send matic from polygon network to the wallet or send ETH to your wallet to use this.