In terms of SEO, all the elements covered above are essential—they create the foundation for a discoverable site.
Beyond that, the body copy of your webpage offers a real opportunity to optimize. There are no character limits, and it gives you your best chance to communicate to search engines what the content represents.
When you begin to write body copy, revisit your keyword research to understand the types of search queries you’re seeking to answer with this content. Your goal should be to write body copy that answers the most common search queries associated with your target keywords. By doing this, you’ll naturally include variations of the keywords in the copy while still creating content that’s designed to serve real people who access your site.
Similarly, if you understand the intent of search queries for your product, you can write in a tone that matches that intent. For example, if you know that people regularly search for specifics on something you sell, your body copy can take a “salesy” tone and include the selling points of your product.
The intent of search queries you target can inform your content choices further still—not just in terms of the copy itself, but also in terms of page design. For example, if certain queries imply that readers want to compare the feature set of one product with another, you could include a comparison table. Or, if a query is of the form “best X for Y,” you could include an ordered list.
Although there are no limitations to the amount of body content you can include (aside from user experience best practices), you want to maximize the value of your time and resources. It’s not a good use of either to write thousands of words for every page on your site, and it won’t provide a good user experience. To gauge the appropriate content length, analyze the existing search results and see what’s already ranking. This should give you an idea of how much content to produce.