# Overview (https://docs.axelar.dev/gmp/integrations/evm/intro) On EVM chains, a contract sends a message by calling `callContract` on Axelar's gateway contract, and receives one by implementing `_execute` from `AxelarExecutable`. The contracts are in [axelar-gmp-sdk-solidity](https://github.com/axelarnetwork/axelar-gmp-sdk-solidity). EVM contracts can exchange messages with every connected chain, not only other EVM chains. To send tokens, use the [Interchain Token Service](https://docs.axelar.dev/llms.mdx/its/overview/content.md). Copy this page with **Copy Markdown** at the top and give it to your agent, with what you want to build or the contract you want to make cross-chain. The copied page links to the Markdown of the other pages it refers to, so the agent can read them too. Review what it writes, and test on testnet before mainnet. ## Message flow [#message-flow] Sending, on the source chain: 1. Your contract pays gas to the [gas service](https://docs.axelar.dev/llms.mdx/gmp/gas/gas-service/content.md) (`payNativeGasForContractCall`). 2. Your contract calls `callContract` on the gateway, which emits a `ContractCall` event. Receiving, on the destination chain: 1. Axelar verifies the event and approves the message on the gateway. 2. A relayer calls `execute` on your contract. 3. `AxelarExecutable` asks the gateway to validate the message, which marks it executed, then calls your `_execute`. ## Consensus and Amplifier chains [#consensus-and-amplifier-chains] EVM chains connect to Axelar in one of two ways (see [Amplifier](https://docs.axelar.dev/llms.mdx/infrastructure/content.md#a-cross-chain-protocol-amplifier)), with a different gateway contract. Contracts that send and receive plain messages work the same way on both: `AxelarExecutable` supports both gateways. | | Consensus chains | Amplifier chains | | -------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------- | | Gateway contract | [`AxelarGateway`](https://github.com/axelarnetwork/axelar-cgp-solidity/blob/main/contracts/AxelarGateway.sol) | [`AxelarAmplifierGateway`](https://github.com/axelarnetwork/axelar-gmp-sdk-solidity/blob/main/contracts/gateway/AxelarAmplifierGateway.sol) | | `callContract` | Yes | Yes | | [`callContractWithToken`](https://docs.axelar.dev/llms.mdx/gmp/integrations/evm/send-tokens-with-messages/content.md) | Yes | No | | Command ID | Assigned by Axelar | `keccak256(sourceChain + "_" + messageId)` | | Approval event | `ContractCallApproved` | `MessageApproved` | [Chains and contracts](https://docs.axelar.dev/llms.mdx/infrastructure/network/chains-and-contracts/content.md) shows each chain's type. The [contract reference](https://docs.axelar.dev/llms.mdx/gmp/integrations/evm/gmp-contracts/content.md) has the details. ## Setup [#setup] Install the SDK: ```bash # npm npm install @axelar-network/axelar-gmp-sdk-solidity # Foundry forge install axelarnetwork/axelar-gmp-sdk-solidity ``` With Foundry, add a remapping so the imports in these docs resolve: ``` @axelar-network/axelar-gmp-sdk-solidity/=lib/axelar-gmp-sdk-solidity/ ``` Your contract needs two addresses on each chain it's deployed to, the gateway and the gas service. Both are on [Chains and contracts](https://docs.axelar.dev/llms.mdx/infrastructure/network/chains-and-contracts/content.md). ### Chain names [#chain-names] Contracts identify chains by their Axelar name, such as `arbitrum` or `base`, not by EVM chain ID. Names are listed on Axelarscan: [mainnet](https://axelarscan.io/resources/chains) | [testnet](https://testnet.axelarscan.io/resources/chains). When sending, chain names are case-insensitive. When receiving, `sourceChain` is the name exactly as the chain was registered, and some older chains were registered capitalized: `Ethereum`, `Avalanche`, `Polygon`, `Fantom` and `Moonbeam`. Compare it to the exact string. The source chain of a message is shown on its Axelarscan page. ## Next steps [#next-steps] * [Send and receive messages](https://docs.axelar.dev/llms.mdx/gmp/integrations/evm/gmp-messages/content.md): a complete contract, and the checks your contract must make. * [Messages with tokens](https://docs.axelar.dev/llms.mdx/gmp/integrations/evm/send-tokens-with-messages/content.md): send a message with gateway tokens, between consensus chains. * [Express](https://docs.axelar.dev/llms.mdx/gmp/integrations/evm/express/content.md): execute messages before the source chain is final. * [Contract reference](https://docs.axelar.dev/llms.mdx/gmp/integrations/evm/gmp-contracts/content.md): gateway functions and events. * [Deployers and libraries](https://docs.axelar.dev/llms.mdx/gmp/integrations/evm/deployers-and-libraries/content.md): deploy to the same address on every chain, and helper libraries. ## Resources [#resources] * [axelar-gmp-sdk-solidity](https://github.com/axelarnetwork/axelar-gmp-sdk-solidity): executables, the Amplifier gateway, deployers and libraries. * [axelar-cgp-solidity](https://github.com/axelarnetwork/axelar-cgp-solidity): the gateway and gas service on consensus chains. * [axelar-examples](https://github.com/axelarnetwork/axelar-examples): example apps. * [axelar-local-dev](https://github.com/axelarnetwork/axelar-local-dev): run cross-chain tests against local chains. --- All pages of these docs, as Markdown: https://docs.axelar.dev/llms.txt