Had a misfire in my 98 F150 4.6. Now there is a metallic rattle at the front of the engine and an occasional knock. Any ideas what to look for? Thank you for the help.

 

i would just turn it on, get under the truck and look

 

Right! and if you still can't locate the problem, -pull the serp belt/ then start. If the noise is no longer there, it's one of the pulleys, AC, clutch fan or something along those lines.

Hope it's nothing internal.

Good Luck and welcome to the site!