Psalm 136 is a hymn of thanksgiving that focuses on God's enduring loving-kindness (Hebrew: chesed). Verse 3, "Give thanks to the Lord of lords; for his loving kindness endures forever," means the following:

"Give thanks to the Lord of lords": This phrase emphasizes God's supreme authority and power. He is not just a lord, but the ultimate Lord, sovereign over all other rulers and powers. We are called to express our gratitude to this supreme being.

"for his loving kindness endures forever": This is the refrain that repeats throughout the entire psalm, highlighting the core message. "Loving kindness" (chesed) encompasses God's steadfast love, mercy, faithfulness, grace, and covenant loyalty. It's not just a passing sentiment but a permanent characteristic of God's nature. The word "endures forever" indicates that this love is constant, unwavering, and eternal.

In essence, the verse encourages us to give thanks to the Almighty God because His loving-kindness is eternal and unchanging. It points to the consistent and reliable nature of God's love as the foundation for our gratitude. This isn't about thanking God for specific blessings in isolation, but acknowledging the bedrock of His character, which informs and empowers all His actions. God's love, mercy, and faithfulness are the reasons why we can trust Him and find hope, no matter what challenges we face.