Tippin.me has had a browser extension for a long time, both for firefox and chrome: https://lightningnetworkstores.com/e/tippin.me . It's custodial, so it's fundamentally different from metamask but the experience comes very close.

Zeus is an open-source wallet that allows you to connect your own node (https://lightningnetworkstores.com/e/zeusln.app). I think it's only a matter of time before they do a browser extension. They seem to have been working hard recently and have dev bounties, maybe they will add a bounty for this.

@57100 There is Lightning Joule that connects to your node: https://lightningjoule.com too!

It has had no updates since late 2019 and has been removed from firefox shop.

Lightning Labs has recently made some advances that make it easier to connect the browser to a LND node (https://twitter.com/roasbeef/status/1422354952186302465).

@6db33