ERC-20 tokens and metamask

I can’t seem to be able to get TETHER on metamask.  I sent some ETH to my metamask wallet.  I then tried to exchange some ETH for TETHER, but the transaction failed.  I tried increasing the gas, that transaction failed.  I then tried using my ledger wallet to buy TETHER in metamask wallet, and that failed as well.  I was able to add the USDT (TETHER) token to my metamask wallet.  There is an option to view the token in etherscan, and that gives a hash labeled “contract”.  I thought that hash would be used like a public key to send ETH, but now I don’t know.  Has anybody done this, or know what I am doing wrong?