Upvote:2
Here's one about householders and the four pleasant mental abidings. But I think this refers to the four rupa jhanas rather than the four brahmaviharas.
From Gihi Sutta (AN 5.179):
Then Anathapindika the householder, surrounded by about 500 lay followers, went to the Blessed One and, on arrival, having bowed down to him, sat to one side. So the Blessed One said to Ven. Sariputta: “Sariputta, when you know of a householder clothed in white, that he is restrained in terms of the five training rules and that he obtains at will, without difficulty, without hardship, four pleasant mental abidings in the here & now, then if he wants he may state about himself: ‘Hell is ended; animal wombs are ended; the state of the hungry shades is ended; states of deprivation, destitution, the bad bourns are ended! I am a stream-winner, steadfast, never again destined for states of woe, headed for self-awakening!’
Not metta specifically but I can find a sutta where the Buddha recommended some lay people to allocate some time to practice jhana meditation.
From the Piti Sutta (AN 5.176):
Then Anathapindika the householder, surrounded by about 500 lay followers, went to the Blessed One and, on arrival, having bowed down to him, sat to one side. As he was sitting there the Blessed One said to him, “Householder, you have provided the community of monks with robes, alms food, lodgings, & medicinal requisites for the sick, but you shouldn’t rest content with the thought, ‘We have provided the community of monks with robes, alms food, lodgings, & medicinal requisites for the sick.’ So you should train yourself, ‘Let’s periodically enter & remain in seclusion & rapture.’ That’s how you should train yourself.”