Sometimes it's good to think of your site as part of the Internet.
In that sense a keyword or keyword phrase would function as a sort of dynamic menu item. Let's call it a keyword question.
A seeker types in a keyword question. For example, "road bike tires tampa." She's asking the question, "Search engine, where can I find out something about road bike tires in Tampa?"
If she could, our seeker might simply click the tab "Road bike tires in Tampa."
If she happens to click your site's url in the search engine results, she'll be taken to a page. If the page helps her to find out about road bike tires in Tampa, she'll read on. She'll form a relationship with you. That could end in a sale.
On the other hand, if she does not see at a glance something useful about road bike tires in Tampa, without giving it a thought, she will return to her search results and click another tab. If she has to contend with a movie, or a song, or extraneous happy talk ("welcome to our tire site"), she'll hit the popular back button and try somewhere else.
Make good landing pages
Make sure your pages answer the questions your seeker is asking. For example, it does no good to optimize your home page for "road bike tires in Tampa" if your homepage is full of branding statements and pictures showing people riding bicycles, but no real information about tires.
What she wants to see is a page that tells her what she wants to know about tires and links to more information on your site if she needs it. It's almost the same as if she pressed a menu tab.