The gotcha that catches everyone: gas is paid in the chain’s own token
The single most important cross-chain concept: you pay transaction fees in the chain’s native token, not in the asset you’re moving. Holding USDT on Arbitrum does not let you send it — you also need ETH on Arbitrum to pay gas. The same applies everywhere:
- Ethereum / Arbitrum / Base / Optimism:
ETHETH for gas. - Polygon PoS:
POLPOL (formerly MATIC) for gas. - Tron:
TRXTRX for gas (this is why USDT users on Tron always need a little TRX). - Solana:
SOLSOL for gas. - Bitcoin:
BTCBTC for gas (and Lightning uses BTC liquidity in channels).
An L2 inherits its security from its L1 but runs its own execution, so it charges fees in its own gas token — which is usually the L1 native asset bridged over (e.g. ETH on Arbitrum). Forgetting this is the most common way to end up with stranded funds: you have the asset but can’t move it because you have no gas token.
Gas on L2s — the native-token rule
Every chain requires its own native token to pay gas — even on an L2. Pick a chain and an asset you hold, then say whether you also hold the gas token. Watch what happens to your ability to move the asset.
- Chain
- Arbitrum (L2)
- L1 or L2?
- L2 (settles to Ethereum)
- Gas token required
- ETH
- USDT availability on Arbitrum (L2)
- Bridged representation (bridge risk)
Takeaway: an L2 inherits security from its L1 but runs its own execution, so it charges fees in its own gas token — usually the L1 native asset bridged over (e.g. ETH on Arbitrum/Base). Holding a stablecoin does not mean you can move it.
Sending an asset to an address on a chain where that asset doesn’t exist (e.g. Ethereum ERC-20 USDT to a Tron address) usually causes a permanent loss. Always confirm both the address and the network match the asset you’re sending. Many wallets now warn you, but the final responsibility is yours.