Configure at Admin Dashboard → Metropolis Theme, then go to Layouts to set the grid widths and allocated positions.
Injected Gantry Gizmos
There are Gizmos that are injected into a site when enabled, and are stacked vertically; which includes: Google Analytics, Page Suffix, Smart Load Images, Typography Shortcodes, Page Class Suffix, RokStyle, Disable Auto Paragraphs and IE7 Redirect.
Configure at Admin Dashboard → → Metropolis Theme, then go to Layouts tab and set the varying Mainbody/Sidebar layout possibilities.
Note: If no widgets are placed to the Sidebar positions, the Mainbody will become full width.