According to vocalist and guitarist James Hetfield during the SirusXM Town Hall, he's written "tons of material" while sitting at home bored out of his mind. Like we all are at this point (the responsible ones, anyway).
"For me, and I don't wanna sound ungrateful, 'cause I know there's a lot of people out there that are struggling because of this COVID… Where I live, it's all service industry. And, obviously, the music industry, it's tough — it's taken a big hit. For us, we're road dogs — we've been out on the road forever — so you're either on the road or you're writing. So the obvious thing is, 'Well, we're not on the road. Start writing.' So, [I've written] tons of material. And I'm sure there's lots of musicians out there that are just, like, 'Okay, what can I do? I'm gonna write and just get into that,' which I love doing."
In the past, bassist Robert Trujillo made it pretty clear in the past that Metallica isn't interested in waiting another six years between records (like between 2008's St. Anger and 2016's Hardwired to Self Destruct). So who knows, maybe we'll get new Metallica next year?