You can receive transactions to addresses starting with both one1 and 0x. However, Metamask does not allow you to send transactions to addresses starting with one1. You will need its' equivalent 0x address as the destination address. For that, follow the procedures below.
For mainnet, go to https://explorer.harmony.one/#/ (Mainnet). For testnet, go to https://explorer.testnet.harmony.one/#/.
Search for your one1 address at the top.
At top of the screen, toggle the address format from ONE to ETH.
Copy the 0x address format by clicking on the small icon right to the address
You now have the 0x address which corresponds to your one1 address.
To send a transaction on MetaMask, click on Send button and on next window paste the destination address starting with 0x, fill the amount you want to send, click on Next, and then click on continue.
In order to receive a transaction, simply share the 0x address format with the sender.
