Is there a specific reason why you want to import/transfer your key to Metamask? If your Trustwallet's wallet is your cold storage ( or your main wallet where you store all of your important coins & tokens), maybe importing the key is not really a good choice.
Just to buy ETH-SOL-based cryptos. But here many people suggested that we can buy ETH based crypto also on TW and we can't buy SOL based on MM. So as of now, I am planning to stick with TW.
Also, I am little bit worried, that I will not be able to add RPC and other tokens. I created MM new account today, I added RPC of BSC, but I was not able to get RECEIVE address of BNB, so I thought it is not my cup of tea. So currently sticking with TW.
In TW, I will learn to buy ETH was tokens.