Can I add Polkadot to my Metamask?
You cannot add the Polkadot network RPC to your Metamask Wallet because Metamask does not support Polkadot's infrastructure.
Polkadot's substrate allows developers to build dapps in different programming languages like JavaScript and Rust. Metamask only supports blockchains written in the solidity programming language, such as the Ethereum Virtual Machine and forks like Avalanche or Fantom.

Will Metamask add Polkadot (DOT) Wallets?
Metamask has not announced any intention to add Polkadot support to their wallets. Their company is run by Consensus, which own Ethereum and is unlikely to support alternative blockchains like Polkadot or Solana.
How to get a Polkadot Wallet
If you want to bridge to the Polkadot network to use their DeFi, GameFi and NFT applications, you will need to download a Parity Signer wallet. It allows you to interact with the DOT blockchain from you iOS or Android mobile, with a locally hosted on-chain Wallet.
Polkadot Wallet vs Metamask Wallet
If you are using a Polkadot Wallet, you will not be able to interact with popular applications on DeFi like OpenSea, Uniswap, Sushiswap, AAVE and many others. This is because these applications only run on the Ethereum blockchain, and other EVM compatible networks.
You can only access popular DeFi and GameFi applications with a Metamask Wallet, because there aren't many dapps on Polkadot.
What is Polkadot?
Polkadot is a decentralized network that enables cross-chain transfers of any type of data or asset. Polkadot is built on a Substrate blockchain framework and utilizes the Parachain architecture to allow for scalability and interoperability between blockchains. Polkadot also uses GRANDPA (Gravity Randomized Agnostic Nebulous Determination Point Accumulator) for finality, which allows it to achieve high transaction speeds.

Polkadot has its own native token, DOT, which is used to secure the network and enable governance. Polkadot was founded by Gavin Wood, co-founder of Ethereum, and is backed by a number of major crypto organizations including Web3 Foundation, Polychain Capital, Fenbushi Capital, and Parity Technologies.
The Polkdatot blockchain is considered to be one of the most promising protocols in the cryptocurrency space due to its unique architecture and ability to enable cross-chain transfers. Polkadot is also one of the few protocols that uses GRANDPA for finality, which allows for high transaction speeds.
Final Thoughts
In short, the Polkadot blockchain cannot be added to Metamask wallets because it is not compatible with the Ethereum Virtual Machine (EVM). However, you can download a Parity Signer Wallet to interact with the DOT blockchain and access popular DeFi and GameFi applications like ANKR, Akala and others.
Additionally, Polkadot has its own native token, DOT, which is used to secure the network and enable governance. Ultimately, Polkadot is one of the most promising blockchains in the crypto space due to its unique architecture and ability to allow for cross-chain transfers.