Axelar has introduced General Message Passing (GMP), enabling users to seamlessly transfer assets between blockchains. Users can securely send their assets by calling Axelar, and Axelar, in turn, executes a transaction on the destination blockchain, symbolizing the transfer of assets to the designated chain. Notably, despite the transaction indicating a transfer, users can retain their assets stored on Axelar.

For example, a user who wants to bridge an NFT from Ethereum to Polygon can call Axelar to make the transaction symbolizing the transfer of assets but keeping their asset on Axelar. This enables users to utilize different blockchains but store their assets on one chain.

According to Most Popular Message Types for Cross-Chain Transfers graphic, cross-chain transfers can have multiple message types. Some message types amassed the same number of transactions.

Based on this fact, I was curious about:

1. Can the same transfer have multiple message types? Why?
2. How do users assign a message type? Can they make their own message type? Are message types specific to specific blockchains?

Holy smokes! The median transfer transaction has over 20 message types. How is this scalable? What is the need for different message types for an individual transaction?