Sure, here are some keywords that could be used to describe songs about various topics:

Love:

Romance
Passion
Heartbreak
Affection
Devotion
Longing
Intimacy
Desire
Connection
Commitment
Friendship:

Companionship
Loyalty
Trust
Support
Memories
Bonding
Togetherness
Camaraderie
Fun
Shared experiences
Nature:

Beauty
Wilderness
Serenity
Tranquility
Seasons
Landscapes
Animals
Plants
Elements (earth, air, water, fire)
Harmony
Social Issues:

Injustice
Equality
Empowerment
Activism
Freedom
Poverty
Discrimination
Unity
Change
Hope
Self-Discovery:

Identity
Growth
Reflection
Transformation
Inner peace
Discovery
Journey
Authenticity
Acceptance
Purpose
Party/ Celebration:

Festivity
Dance
Joy
Excitement
Energy
Happiness
Gathering
Music
Drinks
Fun
Sadness/ Loss:

Grief
Sorrow
Pain
Mourning
Solitude
Melancholy
Regret
Nostalgia
Healing
Resilience
Adventure:

Exploration
Discovery
Courage
Thrill
Wanderlust
Expedition
Risk
Freedom
Excitement
Journey