Is it possible to send eth and add a message in the transaction

Yes, it is possible to attach a message to an Ethereum transaction. However, Ethereum transactions don't natively support text messages in the same way that, for instance, you might attach a memo to a bank transfer. Instead, messages can be included in a transaction's data field, which is primarily used for interacting with smart contracts.

When you send a transaction (including ETH transfers), you can include extra data in the input data field. This data is typically used for contract function calls and is encoded in hexadecimal format. If you want to include a human-readable message, you'll need to convert your text message into hex format and include it in this field.

Here's a basic example of how you might achieve this:

1. Convert your plain text message to hex. For example, "Hello, World!" can be converted to hex as 0x48656c6c6f2c20576f726c6421.

2. Include this hex string in the data field of your Ethereum transaction.

Keep in mind that including additional data may slightly increase the cost of the transaction because it increases the amount of data that needs to be stored on the blockchain. Also, this message will be publicly visible on the blockchain and permanently stored, so it's important not to include any sensitive or private information.

It's worth noting that not all Ethereum wallets or interfaces provide an easy way to add data to a transaction. You may need to use a more advanced wallet or tool that allows you to interact with the data field directly.

Remember that the primary function of the data field is for smart contract interaction, so if you're sending just a simple ETH transfer to a regular address, the recipient may not even notice the attached message unless they look for it specifically using a blockchain explorer or have a wallet that displays transaction input data.