See, now there’s a term I can google and get results.
So LCP is a metric for the biggest thing that took time before document.ready.
Well, which element of your website is the LCP lodestar? For example, if I look at this page in chrome’s performance tab, it tells me that the element is Techno’s image. Which makes sense, the rest of the page is pretty lightweight, and that image is (comparitively) big.