A couple months back the guys at Ignite Amps released another really good-sounding free amp sim plugin called the Anvil.
It features three independent channels, one for clean, one for rhythm and one for lead.
The sim supports stereo and mono routing and the controls can be automated.
There are 3 oversampling settings (2x, 4x, 8x) and it has a preset manager, although no presets are included.
The Anvil is available in VST, VST3, and AU formats for PC and Mac, both 32 and 64 bit systems are supported.
The Anvil is an amp sim only so you’ll need an IR loader and IRs along with it. Luckily Ignite Amps also offers a free IR loader called NadIR that works great.
Their free SHB-1 tube amp plugin for bass is really good too, and so is their Emissary amp sim. Great sims for metal!