Polkadot is its own network, not running on Ethereum or any other chain. Therefore, you can only send DOT to a Polkadot address on the Polkadot network.

Polkadot addresses always start with 1. 

MetaMask is currently working on a Polkadot integration, however it is not available yet. Once available, the Development State in this list of Polkadot wallets will be updated from "building" to "live".

If you sent DOT from Binance to MetaMask (before the official MetaMask DOT integration), you very likely sent a Binance pegged DOT version on the Binance chain. In that case, please contact Binance Customer Support if you need any assistance. Since those transactions do not take place on the Polkadot network, we are unable to assist you here at Polkadot Support. 

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