For a band that helped define thrash metal, expectations are always brutal. Especially when you are talking about Megadeth releasing music from what is being billed as their final studio album. With “Let There Be Shred,” however, there is no confusion, no hesitation, and no mixed message. This is Megadeth doing exactly what they do best. After the uneven reactions to previous singles, “Let There Be Shred” arrives like a punch to the face. Fast, aggressive, riff-driven and un