Glossary: RPC, Gas, Token Allowance, EVM, and Key Terms

Quick intro

This glossary collects clear, actionable definitions for core terms you’ll see while using MetaMask as a software wallet and interacting with DeFi. I use this daily. I’ve made mistakes (approved a bad contract once). And I’ve learned which terms map directly to security actions you can take.

If you want quick links to hands-on articles, see the related pages listed throughout (for example, Custom RPC network settings or Seed phrase backup & recovery).

EVM and EVM-compatible — what that means

EVM stands for Ethereum Virtual Machine. It’s the runtime that executes smart contracts on Ethereum and many other chains. When a chain is EVM-compatible, the same smart contract code and developer tools generally work across it. That matters because MetaMask acts as an EVM-compatible wallet: the same account/address can interact with many EVM chains once the network is added.

Practical implication: switching networks in MetaMask feels like changing a browser tab for the same account. But gas tokens and transaction rules can differ. (Yes — that means you can accidentally send ETH to a token-only chain if you’re not careful.)

RPC — what is rpc metamask?

RPC (Remote Procedure Call) is the way your wallet talks to a blockchain node. In practice MetaMask uses JSON-RPC endpoints to read balances, estimate gas, and send signed transactions (calls like eth_call, eth_sendRawTransaction). "rpc metamask" usually refers to the RPC endpoint MetaMask is configured to use for a given network.

How does RPC affect your wallet experience? Response time, reliability, and what data is available depend on the node. Public node providers are fast and convenient. Running your own node gives better privacy and control. See Custom RPC network settings and Running your own node for configuration and trade-offs.

RPC options comparison:

RPC type	Pros	Cons
Public hosted node	Fast onboarding, global endpoints	Privacy trade-offs, rate limits possible
Custom RPC (third-party)	Pick region, features	Requires vetting and trust
Local node	Maximum control, privacy	Resource and sync cost

Gas fees and EIP-1559 (eip-1559 metamask definition)

Gas fees pay for computation on EVM chains. EIP-1559 reworked how fees are calculated by adding a base fee (burned) and a priority fee (tip) to reward miners/validators. The wallet shows fields like "Max fee" and "Priority fee" — these map to EIP-1559 parameters.

Simple breakdown table:

Field	What it is	Where it shows up
Base fee	Minimum network fee (burned)	Determined by block, not editable
Max priority fee	Tip to validators	Settable in MetaMask
Max fee	Upper limit you pay	Settable (max fee ≥ base fee + priority fee)

Gas estimation is an approximation. Complex contract calls (swaps, approvals, batch transactions) can use more gas than estimated. In my experience, always leave some headroom on "max fee" if timing matters. But be mindful: setting an excessive max fee doesn’t mean you will pay it — the protocol charges only what’s used up to that cap.

L2 networks change the economics. Layer 2 transactions can be much cheaper, but they may require an initial deposit or bridging step. See Gas fees and L2 and Add L2 networks for details.

Accounts: seed phrase and private keys (seed phrase metamask definition, private keys metamask)

Seed phrase definition: a 12- or 24-word seed phrase is the human-readable backup of your wallet that can recreate all your private keys. "seed phrase metamask definition" commonly appears when users ask how to restore an account.

Private keys: each account in MetaMask has a private key that signs transactions. "private keys metamask" searches often mean users want to export a single account key. That is possible for loose (software) accounts; hardware accounts behave differently (see Hardware wallets).

Security checklist: back up your seed phrase offline, never store it in the cloud in plaintext, and treat exported private keys as highly sensitive. If you lose your phone, restore from your seed phrase on another device (see Seed phrase backup & recovery).

Token allowance and approvals (token allowance metamask)

Token allowance (also called token approval) lets a smart contract move tokens on your behalf. Approvals are a common UX in DeFi: connect, approve, then swap. But too-wide allowances (unlimited approvals) increase risk if a contract is malicious.

Want to manage allowances? Use the Token allowances and revoke guide. Short checklist: review approvals after a new dApp connection, revoke approvals you don't need, and prefer single-use approvals for unfamiliar contracts.

dApps, WalletConnect, and in-app providers

MetaMask injects an EVM provider into browser dApps. Mobile apps use in-app browsers or WalletConnect for secure sessions. WalletConnect provides a QR or deep-link handshake so you can use a dApp without exposing your seed phrase to mobile browsers.

Practical note: some mobile dApps ask for signature requests that look identical to transaction approvals. Pause and verify what a signature does before confirming.

Layer 2, bridges, and cross-chain basics (layer 2 metamask)

Layer 2 solutions move transactions off mainnet to reduce gas fees. "layer 2 metamask" queries often ask how to add L2s — usually by adding the network (see Add L2 networks) and bridging assets. Bridges introduce custodial and smart-contract risk. Read bridge audits and prefer well-reviewed bridges.

Account abstraction & smart contract wallets

Account abstraction (smart contract wallets) lets wallets use session keys, gas sponsorship, and batched transactions. That enables gasless UX and finer permissioning (e.g., limit a dApp to spend only a specific token for a duration). See Account abstraction & smart contract wallets for hands-on examples.

How-to: Step by step common tasks

How to add a custom RPC (short):

Open network dropdown in MetaMask.
Click "Add network" → "Custom RPC."
Enter network name, RPC URL, chain ID, currency symbol, and block explorer URL.
Save and switch to the new network.
(See Custom RPC network settings for screenshots.)

How to revoke a token allowance (short):

Go to a revoke tool or the token approvals UI.
Connect with MetaMask (read the modal URL carefully).
Identify the contract with a large allowance.
Revoke or set allowance to zero.
Confirm the transaction and check the resulting approval status.
(Also see Token allowances and revoke.)

FAQ

Q: Is it safe to keep crypto in a hot wallet?
A: Hot wallets like MetaMask are convenient for daily DeFi. But they carry higher risk than hardware wallets. Keep small, active balances in a hot wallet and larger holdings in hardware or cold storage.

Q: How do I revoke token approvals?
A: Use a trusted approvals interface or the built-in token approvals screen (if available). Revoke the specific contract or set the allowance to zero. See step-by-step above and how to revoke approvals.

Q: What happens if I lose my phone?
A: If you have your seed phrase, you can restore your wallet on another device. If you don’t, funds are effectively lost. Back up your seed phrase offline. See Seed phrase backup & recovery.

Q: Can I run my own node for better privacy?
A: Yes. Configuring a local RPC endpoint reduces dependency on public nodes. See Running your own node and Developer RPC guide.

Who this guide is for — and who should look elsewhere

Who this helps: active DeFi users, token traders, and developers using MetaMask across multiple EVM-compatible networks. I use this setup for daily swaps and dApp interactions.

Who should look elsewhere: users seeking custodial convenience only, or those unwilling to manage seed phrases. Consider hardware wallets or custodial services for long-term holdings.

Conclusion & next steps

This glossary should make feature names actionable. Want setup steps? Start with Install & create wallet or try the mobile app setup. If you want deeper troubleshooting or recovery steps, see Seed phrase backup & recovery and Compromised wallet: what to do.

If you have a specific term you want explained or a transaction you want me to walk through (screenshot-descriptions accepted), ask — I’ll add it to this glossary. But for now: back up your seed phrase. And double-check approvals.