Google does use the HTML title tag to determine what pages are about, in order to rank them in search results by taking it as a "communication" about what a page is about. Ofcourse, as we all know there are more critical factors, such as the main content, etc.
It is suggested to keep your title tag in the range of 60 to 65 characters, so that it visually appealing to people searching on search engines and also have a unique title for every page.
Most searchers are searching for information, so in a title tag, it is good to address a problem the target audience has in mind. That is why it is often said that one must write titles for people and not search engines.
I have seen websites using emojis in page titles. From what I know, search engines do not show all emojis (only a subset of them).
I have also observed that Google sometimes rewrites meta descriptions (see, https://developers.google.com/search/blog/2021/08/update-to-generating-page-titles) for which Google uses content from the page and hence make headings that contain variations of your main keyword.
The title tag needs to be optimized around the focus keywords(s), as part of one's on-page SEO practice.