MATIC is the second “native currency” in OpenSea (the world's largest trading venue for NFTs), besides ether. It’s also compatible with MetaMask and a vast number of decentralized finance projects (DeFi) use Polygon for the above mentioned reasons. The most famous DeFi projects are decentralized exchanges (DEX) such as SushiSwap. Although it was built on top of Ethereum, it strives to become a so-called automatic market maker (AMM) with several chains.