Blockchains are an alternative way to make an append only data structure, so it's not clear why you would want to use a merkle tree to create a block chain.
Yes, the term block chain does has a specific technical meaning: a sequence of hashed values where each contains the hash of the previous, similar to the way a git commit includes the hash of its parent commit. But the term blockchain has also taken on a broader colloquial meaning of "log with certain cryptographic properties", which both block chain and merkle tree implementations can satisfy with various advantages and disadvantages. I think it's fair to allow usage of the broader definition.
A blockchain can use Merkle trees in several ways. First, the block header usually contains the Merkle root of all transactions. This makes the header, and in turn the Proof-of-Work, commit to all txs, which helps make the chain immutable.
Second, the header can also directly commit to the UTXO set, simplifying the design of light clients (sadly, Bitcoin doesn't do this).
