There's an element for giving emphasis to text, and it's called the em element. Add <em> and </em>.

<html>
 <body>
  <h1>My favorite things</h1>
  <p>
  Raindrops on <em>roses</em><br>
  Whiskers on kittens<br>
  Bright copper kettles<br>
  Warm woolen mittens
  </p>
 </body>
</html>]]>

Make sure to pick <em>, followed by </em>.