If you are looking to mine Metal, keep in mind that before you do so, invest some time into researching if your setup will actually generate you any profit. Metals price can fluctuate and the amount of miners also plays a great deal in your chances of making a profit. At the current price of MTL, consider how much worth it setting up a mining rig would be. Hardware that would be most powerful for mining would be ASICs which are unfortunately nowadays extremely pricey. If mining with a computer, a GPU won’t generate a large turnout but it might be something for the start when mining Metal. Mining profitability charts can show you how much USD you can make for 1 Mh/s of hash rate. These charts also have the electricity expenses covered. Mining difficulty increases by the number of miners and every time the demand for a larger hash rate increases. Your hash rate is basically how much computing power you are providing for mining new blocks. This takes what is called "block time".
What is an ASIC miner? ASIC mining rigs are machines made of a motherboard, ASIC chip and a cooling system. They're designed specifically to mine a certain cryptocurrency and they do it well. This hardwares purpose is to solve as many cryptographic puzzles at a time. The primary investment into one of these could get paid for in a few months, but there is still a large problem with noise, heat and power demand of these machines besides, they do break down and as the machine runs 24/7, they do wear out.
What is a hashrate. A hash rate is basically a scale of how many guesses for the puzzle your mining setup can make in a given amount of time. The rate is in hashes per second (h/s) and can be decadically moved up (KH/s, MH/s,...).
Ethash is used for encrypting Ethereum and Ethereum Classic. Ethash was built to be ASIC-resistant through memory-hardness (by requiring large memory, standart ASICs couldn’t decrypt the puzzles). Unfortunately for graphics miners, in early 2018 the first ASIC miners for Ethash were introduced on the market and Ethereum eventually lost its decentralization similarly like Bitcoin.
SHA256 (or Secure Hash Algorithm) was originally designed by the NSA back in 2002. Later the algorithm found use within the Bitcoin cryptocurrency and is what runs all Bitcoin based coins. SHA256 is a hash of 256 bits and is what miners decrypt using their mining setups which eventually validates blocks, for what miners are rewarded.
The Scrypt algorithm similarly to Ethash was designed to be ASIC-resistant, but unfortunately ASIC miners for Scrypt have entered the market and cryptocurrencies like Litecoin expect the same fate as Bitcoin or Ethereum.
Cryptocurrencies like bitcoin are already ASICs mined so nowadays mining these with a GPU is useless. If you consider that one of the best GPUs on the market go for around $400 and will give you only about 1 GH/s of power and an Antminer U2 which you’re able to get for around $20 on ebay will provide 2 GH/s, the difference is huge. Always calculate if your desired cryptocurrency is still worth mining on your type of setup.
GPUs are far better at handling parallel processing than CPUs. These computations are basically simple math problems at which GPUs are far better at solving. A CPU is nowadays only usable for mining coins which haven’t been destroyed by ASICs miners. Try calculating your turnout using online calculators like WhatToMine.
The DAG Epoch is what the Ethereum mining difficulty is called. In time, as the currency grows and the amount of miners increases, the mining difficulty grows. As the difficulty increases, also the memory requirements do. Mining with smaller GPUs has become impossible due to this feature which prevents ASICs mining.
Certain mining programs allow mining two cryptocurrencies like Ethereum and Pascal, Decred, etc. simultaneously. This allows you to maintain efficiency while mining both coins. When mining for example Eth+sia, mining both has almost no impact on the Ethereum hashrate. You’re basically getting two coins at once for the same power you provide.