Floats in multicolumn setting

If you use


in a multicols environment, the figure won’t appear. If instead you use


the figure will stretch right across the page (just the same as a figure* in standard LaTeX’s twocolumn option).

It’s possible to have single-column figures and tables with captions, using the [H] placement option introduced by the float package but you might have to fiddle with the placement because they won’t « float », and exhibit other strange behaviours (such as silently running off the end of the column at the end of the multicols environment).

Source: Floats in multicolumn setting