This article is part of our complete series on DeFi. If you're new to the topic, start with the pillar guide: DeFi for Beginners: What Decentralized Finance Is and How to Start.

The DeFi world can look intimidating at first, but many of its core concepts are easier to grasp than they seem. One of them is lending and borrowing: one of the most powerful — and most dangerous if you don't control it — mechanics in crypto.

In this guide you'll learn what lending and borrowing actually mean in DeFi, how the Health Factor (HF) works and why it matters, what happens when you get liquidated and why it hurts, how to apply real strategies without over-leveraging, and which mistakes cost beginners money.

1. What lending and borrowing are

In DeFi you can interact directly with smart contracts to do two things:

Lending

You deposit cryptocurrencies — typically stablecoins like USDC or USDT, though also ETH, BTC or other assets — into a protocol. Other users borrow them by leaving collateral, and you earn variable interest proportional to demand.

Functionally it's like a bank deposit, with four key differences: the interest rate adjusts every block based on supply and demand, there's no bank intermediary, the smart contract custodies the funds, and you can withdraw any time (apart from unbonding periods in some protocols).

Typical yields in 2026:

• USDC / USDT on Aave or Morpho: 2-8% APY depending on market cycle.
• ETH lending: 1-3% APY.
• Stables on more exotic protocols: up to 15-20% APY, but with substantially higher risks.

Borrowing

You borrow crypto by leaving other crypto as collateral. As long as your collateral maintains a value sufficiently above the loan, you keep the position and only pay interest on what you borrowed.

Example: you deposit 10,000 USDC as collateral, borrow 5,000 USDC equivalent in SUI, and trade with that SUI while your USDC keeps generating lending yield. You pay variable interest on the borrowed SUI.

Why borrow instead of just selling? Three common reasons:

1. Get liquidity without selling your main position (useful if you believe your collateral will rise and don't want to sell for tax or conviction reasons).
2. Leverage up buying more of the same asset with what you borrowed ("looping" strategy — more on this below).
3. Capture yield opportunities with borrowed money without putting in fresh capital.

2. Health Factor (HF): the critical metric

The Health Factor is the indicator that tells you how close you are to being liquidated. It's the most important metric you should watch when you have an open borrowing position.

Simplified formula:

HF = (Collateral value × Liquidation Threshold) / Debt value

Interpretation:

• HF > 2: very safe. Wide margin for adverse market moves.
• HF 1.5 - 2: reasonable for an active user watching the position.
• HF 1.2 - 1.5: risk zone. A sharp move can liquidate you.
• HF 1.0 - 1.2: critical zone. Constant vigilance or reduce debt.
• HF ≤ 1.0: automatic liquidation. The protocol sells part of your collateral to repay the debt.

Each asset has its own Liquidation Threshold (typically 70-85% for solid collateral like ETH/wBTC/USDC, lower for volatile collateral). That means you can only borrow up to a percentage of your collateral value.

3. Liquidations: what happens when it triggers

When your HF drops below 1, anyone can call the protocol's liquidation function and buy your collateral at a discount (typically 5-10% off market price) in exchange for repaying part of your debt. This:

• Restores protocol balance (debt reduces until your position's HF goes back above 1).
• Costs you money: you lose the liquidation discount + possible fees.
• Blocks additional fees in some protocols (some charge liquidation fees up to 5% extra).

In practice, being liquidated can mean losing 8-15% of collateralized capital. It's not ruin, but it's a tangible cost.

Typical cases where people get liquidated:

• Over-leveraging (initial HF 1.2) and a collateral dip sends it to HF < 1.
• Ignoring the position during a severe market event (flash crash).
• Trusting oracles that can return atypical prices during low-liquidity moments.

4. Main protocols in 2026

Where serious lending/borrowing happens:

• Aave: oldest, multi-chain, mature governance. >$14B TVL. Excellent for new users due to its clear interface.
• Morpho: optimization layer on top of Aave and Compound. Better rates for both sides (lender and borrower).
• Compound: the other classic giant, focused on Ethereum mainnet.
• MakerDAO / Spark: DAI issuer, very specific lending against DAI/USDS collateral.
• Navi (SUI): dominant lending protocol on SUI, competitive yields.
• Kamino (Solana): the reference on Solana, integrated with xStocks and other assets.

5. Practical strategies

Conservative strategy: yield on stables

You deposit USDC on Aave or Morpho. Earn 2-8% APY. Zero borrowing, zero liquidation risk. Ideal for your portfolio's "dry powder".

Moderate strategy: borrowing for liquidity

You have long-term ETH and don't want to sell. You deposit ETH as collateral, borrow USDC against it (target HF: 2+), use that USDC for living expenses or other investments. If ETH rises, your HF improves. If it drops a lot, watch or repay.

Advanced strategy: looping (leverage)

Deposit ETH → borrow USDC → buy more ETH → re-deposit → borrow more USDC → repeat. Result: leveraged exposure to ETH (typically 1.5x-3x). Lending yield can offset part of debt cost.

It's the strategy with the most upside but also the most risk. A sharp ETH drop can cascade-liquidate you because each loop reduces your safety margin.

Advanced strategy: delta neutral with stablecoins

Some protocols let you lend stables and borrow different stables to capture interest rate differentials. Very low risk if the stablecoins involved are solid, but returns typically 1-3% incremental APY.

6. Common mistakes that cost dearly

• HF too low: never operate with HF < 1.5 if you're not monitoring constantly. Initial HF of 2 lets you sleep at night.
• Highly volatile collateral: using low-cap tokens as collateral is a recipe for liquidation because they can move -30% in a day.
• Ignoring fees: real borrowing cost includes interest + any protocol fee + possible oracle fees on some protocols.
• No exit plan: what will you do if your collateral drops 20%? And 40%? Have answers to those questions before opening the position.
• Operating on unaudited protocols: the extra yield small protocols offer rarely compensates the exploit risk.

7. How to start step by step

1. Create DeFi wallet: Rabby + Ledger ideally. See wallet guide.
2. Buy and send USDC from Binance, Coinbase or OKX to your wallet.
3. Start with lending only on Aave or Morpho. Zero borrowing initially.
4. Learn how your yield moves: how APYs vary, when interest accrues, how it looks on the dashboard.
5. Only when you understand all of the above consider opening a small borrowing position with very loose HF.

Conclusion

Lending and borrowing are DeFi's most important primitives and mastering them opens the door to very powerful strategies — from safe passive yield to sophisticated leverage. But the learning curve is real and mistakes cost tangible money.

The basic rule: the Health Factor is your best friend. If you don't understand it or don't watch it, you're not doing lending/borrowing — you're waiting for a liquidation. Start small, learn slowly, and never leverage with money you can't afford to lose.