How to setup a local Ethereum 1.0 light client using Geth and how to connect it to Metamask.
This main benefit is to not fully rely on third-party infrastructure (i.e Infura) to submit transactions the Ethereum mempool - your light client is actually getting data from full nodes so a full node might be an even better option if you can spare the cash for a 2TB+ SSD (port-merge) - this helps data availability within the network.
Use it at your own risk. Always DYOR regarding distributed systems and crypto.
An update will be released for Ethereum Proof-of-stake post Merge.
Get the latest Geth from https://geth.ethereum.org/downloads/ and unpack it.
Through a terminal
./geth --datadir /Users/myu/code/geth_data --syncmode "light" --http --http.port 8545 --http.api personal,web3,eth,net --http.corsdomain '*'
You can of course replace the --datadir argument by the location of your choice, currently the light client takes < 500 MB of space.
Let the sync proceed, with the light client it's pretty fast (around 15 mins) - you can see if it's syncing if you only have "Imported new block headers" messages on the logs.
Open Metamask, click on the Network drop down which is at the very top, select "Localhost 8545"
You can then try to send a Tx through it to see if it works ! If you are fast enough, you'll see that your Geth client received a transaction in its logs.
That's all folks, happy setup ! :)
Geth 1.10.18
Metamask 10.x
See also : https://ethereum.org/en/developers/tutorials/run-light-node-geth/