Interactive web maps and 3d scenes can be added to StoryMaps in a number of ways. You can use the map content block to add interactive maps from ArcGIS Online and the Living Atlas, the embed content block to add maps created in other mapping software, or the built-in express maps feature to create a map within the StoryMaps software. You can add interactive maps as standalone content blocks in StoryMaps or add them to immersive content blocks (e.g., Sidecar content block, Swipe content block).
The express maps feature can be used to create simple reference maps. Since the express maps feature offers limited functionality, it works best if you want to quickly create and annotate maps. The express maps feature is not a good option if you want to use any of the analytic capabilities of GIS.
Express maps can be used to create quick, simple maps directly within the StoryMaps Builder. Maps created in express maps have limited functionality when compared to ArcGIS Online web maps, but don't require any preexisting knowledge of GIS. They're incredibly useful if you want to quickly create and annotate a map and don't need to conduct any type of spatial analysis. Express maps are saved directly within a single story map, so they can't be exported or reused in other story maps.
Maps created in ArcGIS Online can be added to ArcGIS StoryMaps through the Map, Swipe, Sidecar, and Slideshow content blocks. The simplest presentation option is the Map Content block, which will let you add a single web map (or 3d scene) to your story map.