That's a practical question I've actually wondered about myself when needing a temporary spot for a small delivery. From my experience and checking with municipal guidelines, typical urban trash bin lids aren't designed to hold significant weight. Most standard plastic or metal lids on city-issued bins can generally support 5-10 pounds (2-4.5 kg) without issue – think a small Amazon package, a couple of books, or a takeout bag. They're made to withstand weather and occasional light pressure, not constant heavy loads.
However, I wouldn't recommend making a habit of it. The plastic can weaken over time with sun exposure, and hinges may bend. If your bin is older or visibly cracked, even light packages could cause damage. Delivery drivers sometimes place lightweight envelopes on lids, which is usually fine, but I'd avoid anything heavy or valuable that might fall off when the lid is opened.
A better alternative? If you're expecting a package, consider a small waterproof container beside your bin or a designated delivery spot. It's kinder to your sanitation workers and prevents potential damage to your bin or package. The lid's primary job is keeping odors in and pests out, not serving as a delivery shelf – though in a pinch for that lightweight parcel, it'll probably be okay temporarily.