Destination gas is the native coin you need to pay for actions after a cross-chain swap. If you receive a token but have no gas coin, the token can sit in your wallet until you get some.
How thor swap fees compare with bridge routes helps separate route costs from the balance you need for later. A cross-chain service such as THORSwap can move and swap assets across networks in one flow. The receiving network still sets its own rules for spending what arrives.
Which coin pays for the next move?
Keep the network’s native coin, which is its built-in currency for paying transaction fees. On Ethereum, that coin is ETH; on Solana, it is SOL. Sending or swapping a token usually still requires the native coin, even when the token itself is worth much more.
Think of the received token as a parcel and the gas coin as the postage needed to send it onward. Having the parcel does not pay for the postage. For instance, receiving a stablecoin on Ethereum does not give you ETH for sending that stablecoin to someone else.
The same rule applies on a network that uses a different coin from its parent chain. A token on an Ethereum layer 2, a network built to handle transactions alongside Ethereum, may need that layer’s own gas balance. ETH held on Ethereum mainnet does not automatically pay fees on every layer 2.
How much should I keep?
Keep enough for the next action you expect to take, plus a little room for a second attempt. A simple token transfer often costs less than a swap, which involves a smart contract: code on the network that carries out the trade. Costs rise and fall with network demand and the action’s complexity.
Ethereum.org gives a useful comparison: a basic ETH transfer uses 21,000 units of gas, while a token transfer or swap uses more. Gas is the amount of computing work a transaction needs. Solana’s documentation says each transaction has a base fee of 5,000 lamports per signature, with an optional priority fee; one billion lamports equal one SOL.
Those figures describe network fees, not a promise about what your own transaction will cost. Before sending, check the wallet’s current estimate for the exact action and network. If you plan to swap a token and then send it, check the swap and the later send separately.
What can leave funds stuck?
The common edge case is receiving a token into a fresh wallet on a network where you hold no native coin. You can see the token balance, but a transfer or sale may fail because the wallet cannot pay the fee. A small amount of the native coin sent to that same network can restore access.
Also check that the token arrived on the network you meant to use. The same token name can exist on several networks, and balances on one network cannot pay fees on another. In a thor swap, note the destination network before the exchange and make sure your receiving wallet can hold assets there.
I would decide the next action before starting: hold, send, or swap the received asset. Then keep the right network’s native coin for that action. My practical tip is to leave a modest gas reserve in the destination wallet instead of spending every available coin in the swap.