The default card has a maximum width and will be centered horizontally
You probably want to use the default card inside of a grid or else consider using one of the following card variations.
The maximum size of a card can be changed so that the card always fills 100% of the available horizontal space.
Left and right margins can be removed from the card on mobile-size viewports. This provides extra space for the card content on small viewports where space is so valuable, but the cards no longer looks like cards.
This is typically used with wide cards.
A summary card is a smaller card that aligns to the left edge of its parent. Media inside of summary cards is aligned in the same row as the content.