The Sticky on Scroll plugin for wordpress allows to make any element sticky as soon as the element hits the top of the page. It is commonly used to keep navigation menus at the top of page.
You might have to add little bit of HTML/CSS to work this plugin perfectly for other elements except navigation menu. Make sure you do not select too large elements as sticky.
Always try to add a unique element class/ID for the element you want to set as sticky. For multiple elements you can use class for best results.
For multiple elements you can easily add element ID or classes separated by comma (For eg. #section1, #section2, .header). You can also use any HTML elements as sticky. However adding using ID/class is preferable.
Screenshots
Sticky on scoll form
Twenty Sixteen sticky menu
Twenty Sixteen Settings