h1

<h1 style="text-align:center">your heading</h1> 

font-weight

This property sets how thick or thin characters in text should be displayed.

font-weight: normal|bold|bolder|lighter|initial|inherit|number; 

normal - Defines normal characters. This is default. Same as 400
bold - Defines thick characters. Same as 700
bolder - Defines thicker characters
lighter - Defines lighter characters
initial - Sets this property to its default value.
inherit - Inherits this property from its parent element
number - Any number: 100, 200, 300, 400, 500, 600 ,700, 800, 900